Add a missing icon

The view-refresh-symbolic icon is used in the data list
of the inspector. So ship it in gtk. No need to have
it in the demos, then.

demos/gtk-demo/demo.gresource.xml

@@ -272,7 +272,6 @@
     <file>icons/16x16/actions/go-home.png</file>
     <file>icons/16x16/actions/go-up.png</file>
     <file>icons/16x16/actions/mail-send-receive-symbolic.symbolic.png</file>
-    <file>icons/16x16/actions/view-refresh-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/view-fullscreen-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/document-edit-symbolic.symbolic.png</file>
     <file>icons/16x16/emotes/face-cool.png</file>

demos/widget-factory/widget-factory.gresource.xml

@@ -19,7 +19,6 @@
     <file>icons/16x16/actions/document-send-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/star-new-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/view-grid-symbolic.symbolic.png</file>
-    <file>icons/16x16/actions/view-refresh-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/zoom-in.png</file>
     <file>icons/16x16/actions/zoom-in-symbolic.symbolic.png</file>
     <file>icons/16x16/actions/zoom-original.png</file>