improve language on activity disconnecting & file deletion

[madprime]

Description

Members can delete data from a data source, but only if the data source has been disconnected. This is not clear.

My rationale for this is that the data source, as long as it's still authorized, could (in theory, if not always in practice) re-add data to the account. So it's my feeling that data management should be the responsibility of the data source as long as it's connected – not something a user can fiddle with within their Open Humans account – because I see a strong potential for misunderstandings or confusion to occur.

But the fact that a data source might have data management features is also not clear.

Language can be improved on the activity page to help the user understand what actions they may want to take related to deleting data.

Example

Currently the 23andMe upload page says:

23andMe Upload will update your files as needed. Click here to remove this connection.

This could be improved, e.g.

23andMe Upload will update your files as needed. Some projects may provide the ability to manage your data, check the project's site for information on file management.

Click here to disconnect 23andMe Upload. If a project is disconnected, you can still keep data you've received – or you can choose to delete it at any time.

(But don't necessarily use this exact language! Whatever it says here should be as concise and clear as possible.)