Use non-alpha for PHP 8.4

Author: nikic

.github/workflows/main.yml

@@ -34,7 +34,7 @@ jobs:
          - PHP_VERSION: '8.1'
          - PHP_VERSION: '8.2'
          - PHP_VERSION: '8.3'
-         - PHP_VERSION: '8.4.0alpha4'
+         - PHP_VERSION: '8.4'
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps: