Legacy credentialed users are unable to access datasets (due to bug in `get_credentialed_projects_query`?)

[tompollard]

I should have picked this up during review, but the get_credentialed_projects_query(user): is confusingly named.

The function is checking both of the following:

• whether a user is "credentialed" (i.e. their identity has been checked and approved) and
• whether the user has completed appropriate training

I think this may be related to a recent bug that prevents legacy "credentialed" users from accessing datasets.

https://github.com/MIT-LCP/physionet-build/blob/304e093dc550da8636552dc601d6545c07ffc771/physionet-django/project/authorization/access.py#L23-L50