widget-factory: Don't use Return as accel

This is a bad idea, as it interacts badly with
general use of Return for activation.

demos/widget-factory/widget-factory.c

@@ -1668,7 +1668,6 @@ activate (GApplication *app)
   } accels[] = {
     { "app.about", { "F1", NULL } },
     { "app.quit", { "<Primary>q", NULL } },
-    { "app.open", { "Return", NULL } },
     { "app.open-in", { "<Primary>n", NULL } },
     { "app.cut", { "<Primary>x", NULL } },
     { "app.copy", { "<Primary>c", NULL } },

demos/widget-factory/widget-factory.ui

@@ -3834,7 +3834,7 @@ bad things might happen.</property>
     <section>
       <item>
         <attribute name="label" translatable="yes">Open</attribute>
-        <attribute name="action">app.open</attribute>
+        <attribute name="action">win.open</attribute>
       </item>
     </section>
     <section>