Disable CI for Ruby head

Author: n-rodriguez

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
           - '3.4'
           - '3.3'
           - '3.2'
-          - 'head'
+          # - 'head'
           # - 'jruby'
           - 'truffleruby'