fix X-UA-Compatible headers

RAILS3 includes these for us

Change-Id: I4ee8e558b56d167c7d15e794b5b061aabdcd41b3
Reviewed-on: https://gerrit.instructure.com/30265
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>
QA-Review: Cameron Matheson <cameron@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>