Bump test-unit from 3.5.3 to 3.5.5

Bumps [test-unit](https://github.com/test-unit/test-unit) from 3.5.3 to 3.5.5.
- [Release notes](https://github.com/test-unit/test-unit/releases)
- [Commits](test-unit/test-unit@3.5.3...3.5.5)

---
updated-dependencies:
- dependency-name: test-unit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -8,7 +8,7 @@ GEM
   specs:
     power_assert (2.0.1)
     rake (13.0.6)
-    test-unit (3.5.3)
+    test-unit (3.5.5)
       power_assert
 
 PLATFORMS