app,app/internal/wm: [macOS] refresh context on display change

The NSViewGlobalFrameDidChangeNotification notification is documented to
be fired every time [NSOpenGLContext update] needs to be called.
However, the notification fails to fire on my setup when a window is
moved to a display with a different pixel scale, which leads to
incorrectly sized output.

This change gets rid of the notification and updates the context before
every frame.

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

app/internal/wm/gl_ios.go

@@ -100,6 +100,10 @@ func (c *context) Lock() {}
 
 func (c *context) Unlock() {}
 
+func (c *context) Refresh() error {
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	if C.gio_makeCurrent(c.ctx) == 0 {
 		return errors.New("[EAGLContext setCurrentContext] failed")