Update CI workflow: replace deprecated =~ operator with matches for branch pattern condition

Author: Spomky

.github/workflows/ci.yml

@@ -220,7 +220,7 @@ jobs:
   infection:
     name: "🧬 Mutation Testing"
     needs: [prepare_dependencies, tests]
-    if: ${{ github.ref_name =~ '^[0-9]+\.[0-9]+\.x$' }}
+    if: ${{ github.ref_name matches '^[0-9]+\.[0-9]+\.x$' }}
     runs-on: ubuntu-latest
     container:
       image: ghcr.io/spomky-labs/phpqa:8.4