PLATFORM-75 Remove deprecated WallCopyFollowsTask

This task does not expose a form and the last reference to instantiating
it was deleted in
https://github.com/Wikia/app/commit/309580795b9899ae4c89a245c1070bd03a667f96
Merge pull request #3871 from Wikia/PLATFORM-75-wallcopyfollowstask

PLATFORM-75 Remove deprecated WallCopyFollowsTask