Update actions/upload-artifact version to v4

Author: neildaniels

.github/workflows/continuous-integration.yml

@@ -84,7 +84,7 @@ jobs:
         run: "vendor/bin/phpunit --coverage-clover=coverage.xml"
 
       - name: "Upload coverage file"
-        uses: "actions/upload-artifact@v2"
+        uses: "actions/upload-artifact@v4"
         with:
           name: "phpunit-${{ matrix.php-version }}-${{ matrix.deps }}-${{ hashFiles('composer.lock') }}.coverage"
           path: "coverage.xml"