io/semantic: [API] replace DisabledOp with EnabledOp

The double-negative DisabledOp is harder to understand than a
straightforward EnabledOp. Note that the absence of an EnabledOp
implies still means that the widget is enabled.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/bool.go

@@ -49,7 +49,7 @@ func (b *Bool) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
 			b.changed = true
 		}
 		semantic.SelectedOp(b.Value).Add(gtx.Ops)
-		semantic.DisabledOp(gtx.Queue == nil).Add(gtx.Ops)
+		semantic.EnabledOp(gtx.Queue != nil).Add(gtx.Ops)
 		return w(gtx)
 	})
 	return dims