[keyserver] Delete invalid invite links

Summary:
We have created blobs with invite_invite_ prefix, and we need to delete them.

https://linear.app/comm/issue/ENG-9715/blobs-with-invite-invite-prefix

Depends on D13767

Test Plan: Run the migration and check that the blobs were removed for the links from my keyserver.

Reviewers: kamil, angelika

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13768