Reduce amount of tested environments

Author: numbata

.github/workflows/test.yml

@@ -76,11 +76,11 @@ jobs:
             grape: '~> 2.0.0'
             grape_swagger: 'head'
             grape_entity: '~> 1.0.1'
-          - ruby: 'head'
-            grape: '~> 2.0.0'
-            grape_swagger: 'head'
-            grape_entity: 'head'
 
+          # - ruby: 'head'
+          #   grape: '~> 2.0.0'
+          #   grape_swagger: 'head'
+          #   grape_entity: 'head'
           # - ruby: 'head'
           #   grape: 'head'
           #   grape_swagger: 'head'