Tests: use jQuery variable instead of $

For some reason that works with `amd` but not with builded version

Fixes gh-2909

test/unit/dimensions.js

@@ -488,7 +488,7 @@ QUnit.test( "outside view position (gh-2836)", function( assert ) {
 	].join( "" ),
 	stop = assert.async();
 
-	parent = $( html );
+	parent = jQuery( html );
 	parent.appendTo( "#qunit-fixture" );
 
 	parent.one( "scroll", function() {