Editor: Clean up.

editor/js/Sidebar.Project.Materials.js

@@ -22,7 +22,7 @@ function SidebarProjectMaterials( editor ) {
 	var buttonsRow = new UIRow();
 	container.add( buttonsRow );
 
-	var assignMaterial = new UIButton().setLabel( strings.getKey( 'sidebar/project/Assign' ) );
+	var assignMaterial = new UIButton( strings.getKey( 'sidebar/project/Assign' ) );
 	assignMaterial.onClick( function () {
 
 		var selectedObject = editor.selected;

editor/js/libs/ui.js

@@ -976,14 +976,6 @@ class UIButton extends UIElement {
 
 	}
 
-	setLabel( value ) {
-
-		this.dom.textContent = value;
-
-		return this;
-
-	}
-
 }
 
 class UIProgress extends UIElement {