Fixed audio playback on iOS.
Fixed audio playback on iOS.

GoogleCloudPlatform/woolaroo-language-learning-app,GoogleCloudPlatform/woolaroo-language-learning-app,GoogleCloudPlatform/woolaroo-language-learning-app,GoogleCloudPlatform/woolaroo-language-learning-app,GoogleCloudPlatform/woolaroo-language-learning-app