fix: Update GitHub Actions cache action to v34 to fix deprecation error

Author: JoshuaHungDinh

.github/workflows/tests-php.yml

@@ -31,7 +31,7 @@ jobs:
                 id: get-composer-cache-dir
                 run: |
                     echo "::set-output name=dir::$(composer config cache-files-dir)"
-            -   uses: actions/cache@v2
+            -   uses: actions/cache@v4
                 id: composer-cache
                 with:
                     path: ${{ steps.get-composer-cache-dir.outputs.dir }}