Bump parallel_tests from 3.3.0 to 3.4.0 (#15203)

Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 3.3.0 to 3.4.0.
- [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/v3.3.0...v3.4.0)

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

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

Gemfile.lock

@@ -392,7 +392,7 @@ GEM
       av (~> 0.9.0)
       paperclip (>= 2.5.2)
     parallel (1.20.0)
-    parallel_tests (3.3.0)
+    parallel_tests (3.4.0)
       parallel
     parser (2.7.2.0)
       ast (~> 2.4.1)
@@ -746,7 +746,7 @@ DEPENDENCIES
   paperclip (~> 6.0)
   paperclip-av-transcoder (~> 0.6)
   parallel (~> 1.20)
-  parallel_tests (~> 3.3)
+  parallel_tests (~> 3.4)
   parslet
   pg (~> 1.2)
   pghero (~> 2.7)