remove ruby head test

Author: DannyBen

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
  LC_ALL: en_US.UTF-8 
 
  strategy:
- matrix: { ruby: ['3.0', '3.1', '3.2', head] }
+ matrix: { ruby: ['3.0', '3.1', '3.2'] }
 
  steps:
  - name: Checkout code