fix: remove trailing slash when uploading to S3 with dataset_builder.to_csv_file (#4570)

Author: mkkatica

src/sagemaker/feature_store/dataset_builder.py

@@ -427,7 +427,7 @@ def to_csv_file(self) -> Tuple[str, str]:
         if isinstance(self._base, pd.DataFrame):
             temp_id = utils.unique_name_from_base("dataframe-base")
             local_file_name = f"{temp_id}.csv"
-            desired_s3_folder = f"{self._output_path}/{temp_id}"
+            desired_s3_folder = os.path.join(self._output_path, temp_id)
             self._base.to_csv(local_file_name, index=False, header=False)
             s3.S3Uploader.upload(
                 local_path=local_file_name,