Update bundled_gems

gems/bundled_gems

@@ -2,7 +2,7 @@
 minitest 5.14.3 https://github.com/seattlerb/minitest
 power_assert 2.0.0 https://github.com/ruby/power_assert
 rake 13.0.3 https://github.com/ruby/rake
-test-unit 3.3.9 https://github.com/test-unit/test-unit 3.3.9
+test-unit 3.4.0 https://github.com/test-unit/test-unit 3.4.0
 rexml 3.2.4 https://github.com/ruby/rexml
 rss 0.2.9 https://github.com/ruby/rss 0.2.9
 rbs 1.0.4 https://github.com/ruby/rbs