remove redis caching for wiki_pages_js_env
remove redis caching for wiki_pages_js_env

this was added when STUDENT_PLANNER_ENABLED was added, but the key
did not take @current_user into account, which means the
"View All Pages" link visibility (among other possibilities)
could be displayed when it shouldn't be or vice versa.

we could alternatively add @current_user to the cache key, but
I don't think caching is necessary here. the feature flag is
cached in redis anyhow.

test plan:
 - as a teacher, publish a page (that is not the front page)
   and link to the page from a module
 - disable Pages in course navigation
 - view the page. You should see the "View All Pages" link
   at the top.
 - as a student, view the page (from the module link).
   you should not see "View All Pages".

fixes ADMIN-2265

Change-Id: Id99406f456956f1ebe628dc1b9cc5a0b3f9cd89f
Reviewed-on: https://gerrit.instructure.com/174981
Tested-by: Jenkins
Reviewed-by: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
QA-Review: Mysti Sadler <431d062aff1e8f25416b3a7b732fe6effdb03f9a@instructure.com>
Product-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>

djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms