Bug with new hidden metrics

[happy-looter]

Please double check the logic with the new update regarding Metrics. Metrics can now be hidden. These hidden metrics are still being sent to Google Sheets as columns with all 0's.

[ak--47]

@happy-looter thanks for writing in; we'll take this into consideration.

the behavior of the extension generally mirrors what happens if you "export a report" to CSV (using the mixpanel UI), since this is most compatible format with google sheet's data model.

leaving open for now.