Corrected build args

Author: FromeXo

.github/workflows/docker-build-push.yml

@@ -33,4 +33,4 @@ jobs:
             ${{ secrets.DOCKERHUB_USERNAME }}/extforge-phpdebug:php-${{ env.TAG }}
             ${{ secrets.DOCKERHUB_USERNAME }}/extforge-phpdebug:latest
           build-args: |
-            PHP_VERSION=${{ env.TAG }}
+            PHP_VERSION=PHP-${{ env.TAG }}