Cleaner backtrace for Rspec tests

What does this MR do and why?

When tests fails in rspec and raises active record exception. Backtrace includes several lines from lib/gitlab/database which makes reading backtrace difficult. This commit removes this file from the rspec backtrace so that developer can focus on what really matters in the backtrace

Before

2) Gitlab::BackgroundMigration::BackfillOrganizationIdKeys#perform when deploy key is associated with multiple projects uses organization_id from the first associated project
     Failure/Error: connection.public_send(...)

     ActiveRecord::RecordNotUnique:
       PG::UniqueViolation: ERROR:  duplicate key value violates unique constraint "index_projects_on_project_namespace_id"
       DETAIL:  Key (project_namespace_id)=(108) already exists.
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:127:in `public_send'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:127:in `block in write_using_load_balancer'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:150:in `block in read_write'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:248:in `retry_with_backoff'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:140:in `read_write'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:126:in `write_using_load_balancer'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:61:in `block (2 levels) in <class:ConnectionProxy>'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:127:in `public_send'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:127:in `block in write_using_load_balancer'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:150:in `block in read_write'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:248:in `retry_with_backoff'
     # ./lib/gitlab/database/load_balancing/load_balancer.rb:140:in `read_write'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:126:in `write_using_load_balancer'
     # ./lib/gitlab/database/load_balancing/connection_proxy.rb:78:in `transaction'
     # ./spec/lib/gitlab/background_migration/backfill_organization_id_keys_spec.rb:184:in `block (4 levels) in <top (required)>'
     # ./spec/spec_helper.rb:604:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:564:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:496:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/sidekiq_sharding/validator.rb:42:in `enabled'
     # ./spec/spec_helper.rb:495:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:490:in `block (3 levels) in <top (required)>'
     # ./spec/support/sidekiq_middleware.rb:9:in `with_sidekiq_server_middleware'
     # ./spec/spec_helper.rb:481:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:477:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/application_context.rb:103:in `with_raw_context'
     # ./spec/spec_helper.rb:477:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:448:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/ci/config/feature_flags.rb:38:in `ensure_correct_usage'
     # ./spec/spec_helper.rb:447:in `block (2 levels) in <top (required)>'
     # ./spec/support/system_exit_detected.rb:7:in `block (2 levels) in <main>'
     # ./spec/support/migration.rb:52:in `block (2 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (3 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:60:in `with_cross_joins_prevented'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (2 levels) in <main>'
     # ------------------
     # --- Caused by: ---

After

   ActiveRecord::RecordNotUnique:
       PG::UniqueViolation: ERROR:  duplicate key value violates unique constraint "index_projects_on_project_namespace_id"
       DETAIL:  Key (project_namespace_id)=(122) already exists.
     # ./spec/lib/gitlab/background_migration/backfill_organization_id_keys_spec.rb:184:in `block (4 levels) in <top (required)>'
     # ./spec/spec_helper.rb:604:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:564:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:496:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/sidekiq_sharding/validator.rb:42:in `enabled'
     # ./spec/spec_helper.rb:495:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:490:in `block (3 levels) in <top (required)>'
     # ./spec/support/sidekiq_middleware.rb:9:in `with_sidekiq_server_middleware'
     # ./spec/spec_helper.rb:481:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:477:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/application_context.rb:103:in `with_raw_context'
     # ./spec/spec_helper.rb:477:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:448:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/ci/config/feature_flags.rb:38:in `ensure_correct_usage'
     # ./spec/spec_helper.rb:447:in `block (2 levels) in <top (required)>'
     # ./spec/support/system_exit_detected.rb:7:in `block (2 levels) in <main>'
     # ./spec/support/migration.rb:52:in `block (2 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (3 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:60:in `with_cross_joins_prevented'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (2 levels) in <main>'
     # ------------------
     # --- Caused by: ---
     # PG::UniqueViolation:
     #   ERROR:  duplicate key value violates unique constraint "index_projects_on_project_namespace_id"

References

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Before	After

How to set up and validate locally

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