Correct the .github/workflows/diagnostics.yml

- Update the actions/checkout to version 3
- Update the actions/cache to version 3

Author: stefanheimes

.github/workflows/diagnostics.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: PHP ${{ matrix.php }} ${{ matrix.contao }} Pull source
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           fetch-depth: 0
 
@@ -28,15 +28,15 @@ jobs:
           coverage: none
 
       - name: PHP ${{ matrix.php }} ${{ matrix.contao }} Cache composer cache directory
-        uses: actions/cache@v1
+        uses: actions/cache@v3
         env:
           cache-name: composer-cache-dir
         with:
           path: ~/.cache/composer
           key: ${{ runner.os }}-build-${{ env.cache-name }}
 
       - name: PHP ${{ matrix.php }} ${{ matrix.contao }} Cache vendor directory
-        uses: actions/cache@v1
+        uses: actions/cache@v3
         env:
           cache-name: composer-vendor
         with: