Bump parallel_tests from 3.5.2 to 3.6.0 (#15968)

Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 3.5.2 to 3.6.0.
- [Release notes](https://github.com/grosser/parallel_tests/releases)
- [Changelog](https://github.com/grosser/parallel_tests/blob/master/CHANGELOG.md)
- [Commits](https://github.com/grosser/parallel_tests/compare/v3.5.2...v3.6.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -442,7 +442,7 @@ GEM
       av (~> 0.9.0)
       paperclip (>= 2.5.2)
     parallel (1.20.1)
-    parallel_tests (3.5.2)
+    parallel_tests (3.6.0)
       parallel
     parser (3.0.0.0)
       ast (~> 2.4.1)
@@ -789,7 +789,7 @@ DEPENDENCIES
   paperclip (~> 6.0)
   paperclip-av-transcoder (~> 0.6)
   parallel (~> 1.20)
-  parallel_tests (~> 3.5)
+  parallel_tests (~> 3.6)
   parslet
   pg (~> 1.2)
   pghero (~> 2.8)