Bump test-unit from 3.4.7 to 3.6.1

Bumps [test-unit](https://github.com/test-unit/test-unit) from 3.4.7 to 3.6.1.
- [Release notes](https://github.com/test-unit/test-unit/releases)
- [Commits](test-unit/test-unit@3.4.7...3.6.1)

---
updated-dependencies:
- dependency-name: test-unit
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -88,7 +88,7 @@ GEM
     parallel (1.21.0)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    power_assert (2.0.1)
+    power_assert (2.0.3)
     public_suffix (4.0.6)
     racc (1.6.2)
     rake (13.0.6)
@@ -103,7 +103,7 @@ GEM
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
-    test-unit (3.4.7)
+    test-unit (3.6.1)
       power_assert
     thread_safe (0.3.6)
     typhoeus (1.4.0)