Remove invalid ExportSpriteSheet definition from gui.xml

data/gui.xml

@@ -478,9 +478,6 @@
       <key command="NewSpriteFromSelection" shortcut="Ctrl+Alt+N" mac="Cmd+Alt+N" />
 
       <!-- Commands not associated to menu items and without shortcuts by default -->
-      <key command="ExportSpriteSheet">
-        <param name="source" value="tileset" />
-      </key>
       <key command="NewLayer">
         <param name="tilemap" value="true" />
       </key>
@@ -1099,7 +1096,7 @@
       </item>
       <item command="NewFrame" text="@main_menu.frame_new_frame" />
     </menu>
-      
+
     <menu id="tab_popup_menu">
       <item command="CloseFile" text="@.close" group="tab_close" />
     </menu>

src/app/commands/cmd_export_sprite_sheet.h

@@ -64,9 +64,6 @@ public:
 protected:
   bool onEnabled(Context* context) override;
   void onExecute(Context* context) override;
-  bool isListed(const Params& params, const KeyContext& context) const override {
-    return params.empty();
-  }
 };
 
 } // namespace app