fixes typos in admin_setting_tab_spec.rb

Test Plan:
-just needs to pass jenkins

Change-Id: If574260420978264f568c99801ff04fa735f9372
Reviewed-on: https://gerrit.instructure.com/43797
Reviewed-by: Jahnavi Yetukuri <jyetukuri@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>