fix issue 532 in dataprep (#130)

Author: peiwangdb

Diff for: api-connectors/youtube/videos.json

@@ -63,10 +63,10 @@
                 "type": "string"
             },
             "publishTime": {
-                "target": "$.publishTime",
+                "target": "$.snippet.publishTime",
                 "type": "string"
             }
         },
         "orient": "records"
     }
-}
+}