Bump sidekiq-unique-jobs from 6.0.20 to 6.0.21 (#13367)

Bumps [sidekiq-unique-jobs](https://github.com/mhenrixon/sidekiq-unique-jobs) from 6.0.20 to 6.0.21.
- [Release notes](https://github.com/mhenrixon/sidekiq-unique-jobs/releases)
- [Changelog](https://github.com/mhenrixon/sidekiq-unique-jobs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mhenrixon/sidekiq-unique-jobs/compare/v6.0.20...v6.0.21)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Gemfile.lock

@@ -576,7 +576,7 @@ GEM
       sidekiq (>= 3)
       thwait
       tilt (>= 1.4.0)
-    sidekiq-unique-jobs (6.0.20)
+    sidekiq-unique-jobs (6.0.21)
       concurrent-ruby (~> 1.0, >= 1.0.5)
       sidekiq (>= 4.0, < 7.0)
       thor (~> 0)