Bump actions/cache version to v4 to fix node deprecation warnings

Author: W0rma

.github/workflows/continuous-integration.yml

@@ -88,7 +88,7 @@ jobs:
           tools: "composer:v2,flex"
 
       - name: "Cache dependencies installed with composer"
-        uses: "actions/cache@v3"
+        uses: "actions/cache@v4"
         with:
           path: "~/.composer/cache"
           key: "php-${{ matrix.php-version }}-composer-locked-${{ hashFiles('composer.lock') }}"