closes CNVS-21178
makes sure that we aren't showing users their pseudonyms for
delted authentication providers.
TEST PLAN:
1) create an authentication provider for facebook (For example)
2) get a pseudonym associated with it for a user
3) delete the AAC for facebook
4) confirm you no longer see that pseudonym in /users/self
Change-Id: Idf693b9d3cba616146df87a40c016c2356651806
Reviewed-on: https://gerrit.instructure.com/56530
Tested-by: Jenkins
Reviewed-by: Rob Orton <rob@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>
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