Bump minitest from 5.11.3 to 5.12.0

Bumps [minitest](https://github.com/seattlerb/minitest) from 5.11.3 to 5.12.0.
- [Release notes](https://github.com/seattlerb/minitest/releases)
- [Changelog](https://github.com/seattlerb/minitest/blob/master/History.rdoc)
- [Commits](minitest/minitest@v5.11.3...v5.12.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Gemfile.lock

@@ -37,7 +37,7 @@ GEM
     jwt (2.1.0)
     mime-types (2.99.3)
     mini_portile2 (2.4.0)
-    minitest (5.11.3)
+    minitest (5.12.0)
     multi_json (1.13.1)
     multi_xml (0.6.0)
     multipart-post (2.0.0)