Remove uninitalized from coreaudio backend

uninitialized is being deprecated in favour of
MaybeUninit and friends.

In fact, using mem::zeroed() here is the
initialization method that apple docs recommend.

https://developer.apple.com/documentation/coreaudiotypes/audiostreambasicdescription

src/host/coreaudio/mod.rs

@@ -360,7 +360,7 @@ impl Device {
         };
 
         unsafe {
-            let asbd: AudioStreamBasicDescription = mem::uninitialized();
+            let asbd: AudioStreamBasicDescription = mem::zeroed();
             let data_size = mem::size_of::<AudioStreamBasicDescription>() as u32;
             let status = AudioObjectGetPropertyData(
                 self.audio_device_id,