don't render content notices on full-width pages

test plan:
 0. configure a course navigation LTI tool with full-width launch
 1. start a content import via the API, specifying the parameter
    migration_settings[import_in_progress_notice]=1 **
 2. you should see the import notice on the course front page
 3. you should not see the notice when viewing the full-width
    LTI app

** alternatively, you can just turn on the import-in-progress
   notice in the Rails console, which will give you more time
   to test:

     course.add_content_notice :import_in_progress

   then remove it when you want it to go away:

     course.remove_content_notice :import_in_progress

fixes CNVS-15679

Change-Id: I3171812e0d631eab96ae7d0061280e57abbdcc46
Reviewed-on: https://gerrit.instructure.com/41456
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>