Bump test-unit from 3.6.4 to 3.6.5 in /gemfiles/truffleruby

Bumps [test-unit](https://github.com/test-unit/test-unit) from 3.6.4 to 3.6.5.
- [Release notes](https://github.com/test-unit/test-unit/releases)
- [Commits](test-unit/test-unit@3.6.4...3.6.5)

---
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]

gemfiles/truffleruby/Gemfile.lock

@@ -15,7 +15,7 @@ GEM
     rake (13.2.1)
     rake-compiler (1.2.8)
       rake
-    test-unit (3.6.4)
+    test-unit (3.6.5)
       power_assert
 
 PLATFORMS