Update to latest test-unit

* See https://github.com/test-unit/test-unit/issues/165

gems/bundled_gems

@@ -3,5 +3,5 @@ minitest 5.12.0 https://github.com/seattlerb/minitest
 net-telnet 0.2.0 https://github.com/ruby/net-telnet
 power_assert 1.1.5 https://github.com/k-tsj/power_assert
 rake 13.0.0 https://github.com/ruby/rake
-test-unit 3.3.3 https://github.com/test-unit/test-unit
+test-unit 3.3.4 https://github.com/test-unit/test-unit
 xmlrpc 0.3.0 https://github.com/ruby/xmlrpc