overwrite .amlignore file (#32546)

Author: runhli

sdk/ml/azure-ai-ml/azure/ai/ml/operations/_feature_set_operations.py

@@ -159,6 +159,10 @@ def begin_create_or_update(self, featureset: FeatureSet, **kwargs: Dict) -> LROP
         featureset_copy.properties["featuresetProperties"] = json.dumps(featureset_spec._to_dict())
 
         sas_uri = None
+
+        with open(os.path.join(featureset_copy.path, ".amlignore"), mode="w", encoding="utf-8") as f:
+            f.write(".*")
+
         featureset_copy, _ = _check_and_upload_path(
             artifact=featureset_copy, asset_operations=self, sas_uri=sas_uri, artifact_type=ErrorTarget.FEATURE_SET
         )