remove 'development' flag on sortable name feature

closes CNVS-17621

This commit removes the 'development' bit on the sortable name feature
for the gradebook.

Test plan
- Navigate to course feature flags in a production environment
- The sortable name feature should be visible

Change-Id: I8fe5d340767a97852db272d7bd9509f9b2fe35bf
Reviewed-on: https://gerrit.instructure.com/46178
Product-Review: Bryan Madsen <bryan@instructure.com>
Reviewed-by: Bryan Madsen <bryan@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
contributor code of conduct

Change-Id: Id543e945fdfe721493bfd1470d12b26b1916cca3
Reviewed-on: https://gerrit.instructure.com/46252
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
treesame commit of origin/stable/2014-12-20

Treesame-Commit-Id: b38c691db60b0192116c1e68123c5311a29f397a