Bump minitest from 5.19.0 to 5.20.0

Bumps [minitest](https://github.com/minitest/minitest) from 5.19.0 to 5.20.0.
- [Changelog](https://github.com/minitest/minitest/blob/master/History.rdoc)
- [Commits](minitest/minitest@v5.19.0...v5.20.0)

---
updated-dependencies:
- dependency-name: minitest
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -412,7 +412,7 @@ GEM
     mini_magick (4.12.0)
     mini_mime (1.1.5)
     mini_portile2 (2.8.5)
-    minitest (5.19.0)
+    minitest (5.20.0)
     minitest-fail-fast (0.1.0)
       minitest (~> 5)
     minitest-stub-const (0.6)