Fix RSpec/LeakyConstantDeclaration cop violations

!27368 (merged) will enable RSpec/LeakyConstantDeclaration cop while ignoring current violations. These current violations will be fixed in separate MRs and will be tracked here.

Remaining offenses

• spec/db/schema_spec.rb
• spec/lib/gitlab/config/entry/simplifiable_spec.rb
• spec/lib/gitlab/quick_actions/dsl_spec.rb
• spec/lib/marginalia_spec.rb
• spec/mailers/notify_spec.rb
• spec/models/concerns/batch_destroy_dependent_associations_spec.rb
• spec/models/concerns/bulk_insert_safe_spec.rb
• spec/models/concerns/bulk_insertable_associations_spec.rb
• spec/models/concerns/triggerable_hooks_spec.rb
• spec/models/repository_spec.rb
• spec/services/clusters/applications/check_installation_progress_service_spec.rb
• spec/support/shared_examples/quick_actions/issuable/issuable_quick_actions_shared_examples.rb

MRs

!27630 (merged) (Beginning of ee/spec/**/*.rb violations)
!27956 (merged) (More ee/spec/**/*.rbviolations)
!28483 (merged) (Finishes ee/)
!30226 (merged) (qa/**/*.rb)
!30664 (merged) (spec/features and spec/config)
!31792 (merged)