Fix LDAP logo on "Add Auth Provider" page
Summary:
Avoid falling back to the default "user" logo also used for "Username/Password" auth by pointing to the correct logo name for the LDAP provider.
Closes T16156
Test Plan: Go to http://phorge.localhost/auth/config/new/ and scroll to the "LDAP" item, compare the logo/icon before and after applying this patch.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T16156
Differential Revision: https://we.phorge.it/D26157