fix(auth): Fixed bug that sets email to nil on iOS when the User has no provider. (#8209)

Author: russellwheatley

packages/firebase_auth/firebase_auth/ios/Classes/FLTFirebaseAuthPlugin.m

@@ -1252,12 +1252,6 @@ + (NSMutableDictionary *)getNSDictionaryFromUser:(FIRUser *)user {
   NSMutableDictionary *userData = [[self getNSDictionaryFromUserInfo:user] mutableCopy];
   NSMutableDictionary *metadata = [NSMutableDictionary dictionary];
 
-  // This code is necessary to avoid an iOS issue where when unlinking the `password` provider
-  // the previous email still remains on the currentUser.
-  if ([user.providerData count] == 0) {
-    userData[@"email"] = [NSNull null];
-  }
-
   // metadata.creationTimestamp as milliseconds
   long creationDate = (long)([user.metadata.creationDate timeIntervalSince1970] * 1000);
   metadata[@"creationTime"] = @(creationDate);