Fixes juce-framework#1294

https://developer.apple.com/documentation/avfaudio/avaudiosessioncategoryoptions/avaudiosessioncategoryoptionallowairplay

Apple's documentation states that "You can only explicitly set this option if the audio session’s category is set to AVAudioSessionCategoryPlayAndRecord."

Change the code so that it's only explicitly enabled in that specific category.

modules/juce_audio_devices/native/juce_Audio_ios.cpp

@@ -276,7 +276,7 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
 
     static void setAudioSessionCategory (NSString* category)
     {
-        NSUInteger options = AVAudioSessionCategoryOptionAllowAirPlay;
+        NSUInteger options = 0;
 
        #if ! JUCE_DISABLE_AUDIO_MIXING_WITH_OTHER_APPS
         options |= AVAudioSessionCategoryOptionMixWithOthers; // Alternatively AVAudioSessionCategoryOptionDuckOthers
@@ -285,7 +285,8 @@ struct iOSAudioIODevice::Pimpl final : public AsyncUpdater
         if (category == AVAudioSessionCategoryPlayAndRecord)
         {
             options |= AVAudioSessionCategoryOptionDefaultToSpeaker
-                     | AVAudioSessionCategoryOptionAllowBluetooth;
+                     | AVAudioSessionCategoryOptionAllowBluetooth
+                     | AVAudioSessionCategoryOptionAllowAirPlay;
 
             if (@available (iOS 10.0, *))
                 options |= AVAudioSessionCategoryOptionAllowBluetoothA2DP;