Add spec coverage to new "dismissed before" callout methods

About

This issue came out of this discussion !121988 (comment 1409467019).

!121988 (merged) has added some new code to Core classes that should have unit tests written for it.

We technically have coverage through the EE specs that were added, however, once the code suggestions call out feature is removed, those specs will be removed, and we're likely to end up with these changes in Core without any spec coverage.

Because there was urgency in the MR that introduced the code, this task has been left as a follow-up.

Proposal

Add unit tests for the changes made in !121988 (merged) to:

• app/helpers/users/callouts_helper.rb
• app/models/users/calloutable.rb
• app/models/user.rb