Stop requiring sidekiq_middleware in development fixtures that don't need it

Summary

Some DB fixture files (in db/fixtures/development and ee/db/fixtures/development) require './spec/support/sidekiq_middleware', which does nothing currently.

Improvements

Running the fixtures in the Omnibus docker image fails currently since the docker image does not include the spec folder.

Risks

Since requiring './spec/support/sidekiq_middleware' doesn't actually start using the middleware, I don't think the fixtures will break.

As noted in #300613 (comment 499638644), requiring spec/support/sidekiq_middleware also requires sidekiq/testing which changes Sidekiq to testing mode where no jobs are enqueued in Redis. So, if any fixtures use Sidekiq, they might be affected by the removal of ./spec/support/sidekiq_middleware.

Involved components

• db/fixtures/development/09_issues.rb
• db/fixtures/development/20_nested_groups.rb
• db/fixtures/development/06_teams.rb
• db/fixtures/development/16_protected_branches.rb
• db/fixtures/development/25_api_personal_access_token.rb - !52908 (merged)
• db/fixtures/development/24_forks.rb
• db/fixtures/development/13_comments.rb
• db/fixtures/development/14_pipelines.rb
• db/fixtures/development/11_keys.rb
• db/fixtures/development/01_admin.rb
• db/fixtures/development/19_environments.rb
• db/fixtures/development/10_merge_requests.rb
• db/fixtures/development/15_award_emoji.rb
• db/fixtures/development/07_milestones.rb
• db/fixtures/development/17_cycle_analytics.rb
• db/fixtures/development/29_instance_statistics.rb
• db/fixtures/development/12_snippets.rb
• db/fixtures/development/03_project.rb
• ee/db/fixtures/development/20_burndown.rb
• ee/db/fixtures/development/32_compliance_dashboard_merge_requests.rb
• ee/db/fixtures/development/20_vulnerabilities.rb
• ee/db/fixtures/development/90_productivity_analytics.rb
• ee/db/fixtures/development/30_customizable_cycle_analytics.rb