Use mw.msg() for parameter substitution

mw.msg() has already a parameter substitution of $1.
A separate .replace( '$1', ... ) is not necessary.

Change-Id: Ie77bddc4dfb60df36211ce821c1a6f7223cde706

resources/js/ext.uls.ime.js

@@ -301,7 +301,7 @@
 			helpHandler: function ( ime ) {
 				return $( '<a>' )
 					.attr( {
-						href: mw.msg( 'uls-ime-helppage' ).replace( '$1', ime ),
+						href: mw.msg( 'uls-ime-helppage', ime ),
 						target: '_blank',
 						title: $.i18n( 'ext-uls-ime-help' )
 					} )