Bump CI action/cache

Author: fabpot

.github/workflows/documentation.yml

@@ -33,7 +33,7 @@ jobs:
                 run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
 
             -   name: Cache dependencies
-                uses: actions/cache@v3
+                uses: actions/cache@v4
                 with:
                     path: ${{ steps.composercache.outputs.dir }}
                     key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}