Bump minitest from 5.17.0 to 5.18.0

Bumps [minitest](https://github.com/seattlerb/minitest) from 5.17.0 to 5.18.0.
- [Release notes](https://github.com/seattlerb/minitest/releases)
- [Changelog](https://github.com/minitest/minitest/blob/master/History.rdoc)
- [Commits](minitest/minitest@v5.17.0...v5.18.0)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -10,7 +10,7 @@ GEM
     ast (2.4.2)
     docile (1.4.0)
     json (2.6.3)
-    minitest (5.17.0)
+    minitest (5.18.0)
     parallel (1.22.1)
     parser (3.2.1.0)
       ast (~> 2.4.1)