switch link_to block helper to rails 3 format

'<% link_to' to '<%= link_to'

Change-Id: I71fa45f9c59ce7cc685bc05242f4f22750ab43a6
Reviewed-on: https://gerrit.instructure.com/30014
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>