Properly tear down the reachabilityRef in RCTNetInfo

Summary: The pull request that added this (facebook#17397) simply forgot to remove the callback, which would cause crashes if the RCTNetInfo module was ever deallocated. While that usually doesn't happen in apps, it can if the user logs out and you need to wipe all the RCT modules (to remove user data, for instance).

Reviewed By: PeteTheHeat

Differential Revision: D7322999

fbshipit-source-id: e49ec7311b39920f7b7743a5854c0dda1dbccc73

RCTNetInfo.m

@@ -164,6 +164,7 @@ - (BOOL)setReachabilityStatus:(SCNetworkReachabilityFlags)flags
                   reject:(__unused RCTPromiseRejectBlock)reject)
 {
   SCNetworkReachabilityRef reachability = [self getReachabilityRef];
+  SCNetworkReachabilityUnscheduleFromRunLoop(reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
   CFRelease(reachability);
   resolve(@{@"connectionType": _connectionType ?: RCTConnectionTypeUnknown,
             @"effectiveConnectionType": _effectiveConnectionType ?: RCTEffectiveConnectionTypeUnknown,