Bump test-unit from 3.6.4 to 3.6.7 in /gemfiles/typecheck

Bumps [test-unit](https://github.com/test-unit/test-unit) from 3.6.4 to 3.6.7.
- [Release notes](https://github.com/test-unit/test-unit/releases)
- [Commits](test-unit/test-unit@3.6.4...3.6.7)

---
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/typecheck/Gemfile.lock

@@ -100,7 +100,7 @@ GEM
       yard-sorbet
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
-    test-unit (3.6.4)
+    test-unit (3.6.7)
       power_assert
     thor (1.3.2)
     tzinfo (2.0.6)