Revert "Add a MediaWiki preference for enabling ULS IME"

This reverts commit 6ae0fe3e449920d91a85486dc55ec3c6252a9d18.
The commit was duplicating the preferences in 2 places
making the syncing hard.
As per discussion with Pau, we will try alternate approach.

Bug: 48642
Change-Id: I5c97838ed875364dc35b66a3d6c33d9975b5107e
Merge "Revert "Add a MediaWiki preference for enabling ULS IME""