Re-enable PHPStan job

Closes #3415291

.gitlab-ci.yml

@@ -122,6 +122,12 @@ phpcs:
     # Use core's PHPCS configuration.
     - cp $_WEB_ROOT/core/phpcs.xml.dist .
 
+phpstan:
+  before_script:
+    # Ensure our PHPStan configuration has the correct include path to core's PHPStan configuration.
+    - sed -i "s#%rootDir%/../../../#%rootDir%/../../../$_WEB_ROOT/#" $MODULE_DIR/phpstan.neon
+    - cat $MODULE_DIR/phpstan.neon
+
 phpunit:
   parallel:
     matrix: