fix(predictions): use serial queue for WebSocketSession delegate queu… #464

Job	Run time
Build Amplify Swift for iOS / Build Amplify-Build \| iOS	8m 53s
Build Amplify Swift for macOS / Build Amplify-Build \| macOS	5m 36s
Build Amplify Swift for tvOS / Build Amplify-Build \| tvOS	4m 32s
Build Amplify Swift for watchOS / Build Amplify-Build \| watchOS	10m 15s
Confirm Passing Build Steps	1s
	29m 17s

Provide feedback