Update minitest: 5.15.0 → 5.18.0 (minor) (#103)

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

Author: depfu[bot]

Gemfile.lock

@@ -116,7 +116,7 @@ GEM
     method_source (1.0.0)
     mini_mime (1.1.2)
     mini_portile2 (2.8.0)
-    minitest (5.15.0)
+    minitest (5.18.0)
     momentjs-rails (2.20.1)
       railties (>= 3.1)
     nio4r (2.5.8)