Update minitest: 5.15.0 → 5.18.0 (minor) (#19)

Co-authored-by: depfu[bot] <23717796+depfu[bot]@users.noreply.github.com>

Author: depfu[bot]

Gemfile.lock

@@ -8,7 +8,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     http_headers-utils (0.2.0)
-    minitest (5.15.0)
+    minitest (5.18.0)
     rake (13.0.6)
 
 PLATFORMS