ci: use new output command

See: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Author: JaZo

.github/workflows/tests.yml

@@ -38,7 +38,7 @@ 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@v3