MDL-37566 AJAX Only set max-height for chooser dialogues

If we set height as well as max-height then there is a potential for
whitespace to be shown at the bottom of the list of choices.

This commit stops removing the height option so that we only rely upon
max-height for dialogue heigh calculation.

lib/yui/chooserdialogue/chooserdialogue.js

@@ -237,8 +237,7 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
             // new max-height
             var totalheight = newheight;
             newheight = newheight - (15 + 15 + 40 + 40);
-            dialogue.setStyle('max-height', newheight + 'px');
-            dialogue.setStyle('height', newheight + 'px');
+            dialogue.setStyle('maxHeight', newheight + 'px');
 
             // Re-calculate the location now that we've changed the size
             var dialoguetop = Math.max(12, ((winheight - totalheight) / 2)) + offsettop;