Remove support for MediaWiki <= 1.39

With release of MediaWiki 1.41 we no longer need to support MW 1.39

Bug: T355105
Change-Id: I7957ca8aefee168ef11bc20905abd9944faecd73

resources/js/ext.uls.preferences.js

@@ -28,8 +28,7 @@
 		// https://www.mediawiki.org/wiki/Manual:Coding_conventions/JavaScript#Keys
 		this.preferenceName = 'uls-preferences';
 		this.username = mw.user.getName();
-		// For MW < 1.40. ext.uls.isNamed is inlined here to avoid dependency on ext.uls.common.
-		this.isNamed = typeof mw.user.isNamed === 'function' ? mw.user.isNamed() : !mw.user.isAnon();
+		this.isNamed = mw.user.isNamed();
 		this.preferences = null;
 		this.init();
 	};