Add comment explaining override() necessity in test setUp

AppMetaModule bindings must take precedence over PackageModule's
bindings installed by AppModule for OPTIONS requests to work.

Author: koriym

tests/OptionsParamTest.php

@@ -24,6 +24,7 @@ protected function setUp(): void
         $meta = new Meta('FakeVendor\FakeProject');
         $appMetaModule = new AppMetaModule($meta);
         $appModule = new \FakeVendor\FakeProject\Module\AppModule($meta, $appMetaModule);
+        // AppMetaModule bindings (AppName etc.) must take precedence over PackageModule's
         $appModule->override($appMetaModule);
         $injector = new Injector($appModule);