cocoa-cb: render on main queue instead of dedicated queue

initially we drew on a dedicated render queue to circumvent certain
bottlenecks on the main queue, like concurrent events that could lead
to late drawing.

though due to the way cocoa works we need to draw an the main queue
otherwise we get undefined behaviour that could lead to crashes.

Fixes #10276

video/out/mac/gl_layer.swift

@@ -82,8 +82,6 @@ class GLLayer: CAOpenGLLayer {
     enum Draw: Int { case normal = 1, atomic, atomicEnd }
     var draw: Draw = .normal
 
-    let queue: DispatchQueue = DispatchQueue(label: "io.mpv.queue.draw")
-
     var needsICCUpdate: Bool = false {
         didSet {
             if needsICCUpdate == true {
@@ -239,7 +237,7 @@ class GLLayer: CAOpenGLLayer {
 
     func update(force: Bool = false) {
         if force { forceDraw = true }
-        queue.async {
+        DispatchQueue.main.async {
             if self.forceDraw || !self.inLiveResize {
                 self.needsFlip = true
                 self.display()