R1:fb822ba84999

Update Facebook icon on Auth Provider page

Summary: Closes T15545

Test Plan: Go to `/auth/config/new/` in browser and look at icons.

Reviewers: O1 Blessed Committers, Cigaryno, avivey

Reviewed By: O1 Blessed Committers, Cigaryno, avivey

Subscribers: avivey, speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15545

Differential Revision: https://we.phorge.it/D25342