remove old code in user model

Change-Id: Iebd2bda316925c4a3a6210abe636cbc4101b525d
Reviewed-on: https://gerrit.instructure.com/31126
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>
QA-Review: Landon Wilkins <lwilkins@instructure.com>