[skip ci] Remove PHP-8.1 from push.yml triggers (GH-21157)

Author: jorgsowa

.github/workflows/push.yml

@@ -12,7 +12,6 @@ on:
       - .cirrus.yml
       - .circleci/**
     branches:
-      - PHP-8.1
       - PHP-8.2
       - PHP-8.3
       - PHP-8.4