Update RNZeroconf.m
Update RNZeroconf.m

As RN will change the behaviour: ```In a future release React Native will default to initializing all native modules on a background thread unless explicitly opted-out of. RN Zeroconf requires main queue setup since it overrides `init` but doesn't implement `requiresMainQueueSetup`.```
Apercu/react-native-zeroconf,Apercu/react-native-zeroconf