[keyserver] Fix usersToUpdate logic in deleteAccount

Summary: Was looking at this when working on UPDATE_USER updates for updateUserAvatar and it looks like it wasn't actually excluding anything.

Test Plan:
Tested updated logic in updateUserSettings.

Before:

After:

(85999 is viewer.id)

Reviewers: ashoat, ginsu

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7677