Update minitest requirement from ~> 5.20.0 to ~> 5.21.1

Updates the requirements on [minitest](https://github.com/minitest/minitest) to permit the latest version.
- [Changelog](https://github.com/minitest/minitest/blob/master/History.rdoc)
- [Commits](minitest/minitest@v5.20.0...v5.21.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -44,7 +44,7 @@ GEM
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     mini_portile2 (2.8.4)
-    minitest (5.20.0)
+    minitest (5.21.1)
     mocha (2.1.0)
       ruby2_keywords (>= 0.0.5)
     nokogiri (1.15.4)
@@ -104,7 +104,7 @@ PLATFORMS
 DEPENDENCIES
   erb_lint (~> 0.5.0)
   erblint-github!
-  minitest (~> 5.20.0)
+  minitest (~> 5.21.1)
   mocha (~> 2.1.0)
   rake (~> 13.1.0)
   rubocop (= 1.59.0)

erblint-github.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.authors = ["GitHub Open Source"]
 
   s.add_development_dependency "erb_lint", "~> 0.5.0"
-  s.add_development_dependency "minitest", "~> 5.20.0"
+  s.add_development_dependency "minitest", "~> 5.21.1"
   s.add_development_dependency "mocha", "~> 2.1.0"
   s.add_development_dependency "rake", "~> 13.1.0"