Remove Ruby 2.5 from CI matrix

This version is EOL and no longer supported.

Author: ivoanjo

.github/workflows/test.yml

@@ -14,7 +14,6 @@ jobs:
           - macos-latest
           - windows-latest
         ruby-version:
-          - "2.5"
           - "2.6"
           - "2.7"
           - jruby