Welcome: Remove unused image

mode_edit_mask.png must have been added there by mistake

Change-Id: I94c0380f267f473c1ae1347f567ea959f0752496
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/welcome/welcome.qrc

@@ -8,7 +8,6 @@
         <file>images/blogs@2x.png</file>
         <file>images/community.png</file>
         <file>images/community@2x.png</file>
-        <file>images/mode_edit_mask.png</file>
         <file>images/open.png</file>
         <file>images/open@2x.png</file>
         <file>images/project.png</file>