Revert "Add a MediaWiki preference for enabling ULS IME"

This reverts commit 6ae0fe3e44.
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

UniversalLanguageSelector.i18n.php

@@ -30,7 +30,6 @@ $messages['en'] = array(
 	'uls-desc' => 'Gives the user several ways to select a language and to adjust language settings',
 
 	'uls-plang-title-languages' => 'Languages',
-	'uls-ime-enable-preferences-label' => 'Enable input methods',
 );
 
 /** Message documentation (Message documentation)
@@ -43,7 +42,6 @@ $messages['qqq'] = array(
 	'uls-plang-title-languages' => 'A title for the are in the sidebar in which the interlanguage links are supposed to appear.
 This title is shown when there are no interlanguage links there, but an icon that enables the ULS is shown.
 {{Identical|Language}}',
-	'uls-ime-enable-preferences-label' => 'Used as a label for the checkbox in {{msg-mw|Preferences}} page.',
 );
 
 /** Arabic (العربية)