(core) Fixing bug with clearing session on Redis

Summary:
In SAAS build session wasn't cleared after auth provider was
changed. This isn't a problem for SAAS as the provider can't
be changed there, but SAAS build is also used for testing `ext`
code which failed in this situation.

What changed:
- connect-redis version was changed to match grist-core
- clearAsync that is there wasn't working with no session, which  is now patched

Test Plan: Added a test  was reproducing this issue

Reviewers: dsagal

Reviewed By: dsagal

Subscribers: dsagal

Differential Revision: https://phab.getgrist.com/D5034