test(cx-api): add S3_DEPLOYMENT_DEFAULT_MEMORY_LIMIT to feature flag test

- Add new feature flag to expected defaults in features.test.ts
- Feature flag defaults to false (disabled) for backward compatibility
- Fixes CI test failure for feature flag defaults validation

Author: Jamie Yang

packages/aws-cdk-lib/cx-api/test/features.test.ts

@@ -51,6 +51,7 @@ test('feature flag defaults may not be changed anymore', () => {
     [feats.USE_CDK_MANAGED_LAMBDA_LOGGROUP]: false,
     [feats.SIGNER_PROFILE_NAME_PASSED_TO_CFN]: false,
     [feats.ECS_PATTERNS_SEC_GROUPS_DISABLES_IMPLICIT_OPEN_LISTENER]: false,
+    [feats.S3_DEPLOYMENT_DEFAULT_MEMORY_LIMIT]: false,
 
   });
 });