Fix action warning

Author: NielBuys

.github/workflows/test-phpunit.yml

@@ -129,7 +129,7 @@ jobs:
 
       - name: Get composer cache directory
         id: composer-cache
-        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
       - name: Cache composer dependencies
         uses: actions/cache@v4
         with: