QmlDesigner: Remove unused "split editor" icon pngs

The handling of form editor and code editor are now done via the docking
system, the png are unused.

Amends: 1a8c802f56

Change-Id: Iecddc4f68f605abcaad1b9072a128a247f344349
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

src/plugins/qmldesigner/components/resources/resources.qrc

@@ -5,9 +5,5 @@
         <file>formeditorstylesheet.css</file>
         <file>centerwidget.css</file>
         <file>dockwidgets.css</file>
-        <file>images/spliteditorhorizontally.png</file>
-        <file>images/spliteditorhorizontally@2x.png</file>
-        <file>images/spliteditorvertically.png</file>
-        <file>images/spliteditorvertically@2x.png</file>
     </qresource>
 </RCC>