Revert "Rollback to test-unit 3.7.3"

This reverts commit c17307a.

Author: hsbt

NEWS.md

@@ -378,8 +378,8 @@ The following bundled gems are updated.
   * 2.0.5 to [v3.0.0][power_assert-v3.0.0], [v3.0.1][power_assert-v3.0.1]
 * rake 13.3.1
   * 13.2.1 to [v13.3.0][rake-v13.3.0], [v13.3.1][rake-v13.3.1]
-* test-unit 3.7.3
-  * 3.6.7 to [3.6.8][test-unit-3.6.8], [3.6.9][test-unit-3.6.9], [3.7.0][test-unit-3.7.0], [3.7.1][test-unit-3.7.1], [3.7.2][test-unit-3.7.2], [3.7.3][test-unit-3.7.3]
+* test-unit 3.7.5
+  * 3.6.7 to [3.6.8][test-unit-3.6.8], [3.6.9][test-unit-3.6.9], [3.7.0][test-unit-3.7.0], [3.7.1][test-unit-3.7.1], [3.7.2][test-unit-3.7.2], [3.7.3][test-unit-3.7.3], [3.7.4][test-unit-3.7.4], [3.7.5][test-unit-3.7.5]
 * rexml 3.4.4
 * rss 0.3.2
   * 0.3.1 to [0.3.2][rss-0.3.2]
@@ -756,6 +756,8 @@ A lot of work has gone into making Ractors more stable, performant, and usable.
 [test-unit-3.7.1]: https://github.com/test-unit/test-unit/releases/tag/3.7.1
 [test-unit-3.7.2]: https://github.com/test-unit/test-unit/releases/tag/3.7.2
 [test-unit-3.7.3]: https://github.com/test-unit/test-unit/releases/tag/3.7.3
+[test-unit-3.7.4]: https://github.com/test-unit/test-unit/releases/tag/3.7.4
+[test-unit-3.7.5]: https://github.com/test-unit/test-unit/releases/tag/3.7.5
 [rss-0.3.2]: https://github.com/ruby/rss/releases/tag/0.3.2
 [net-ftp-v0.3.9]: https://github.com/ruby/net-ftp/releases/tag/v0.3.9
 [net-imap-v0.5.9]: https://github.com/ruby/net-imap/releases/tag/v0.5.9