fix: ios enrollmentDate -> enrollmentTime

rename `enrollmentDate` -> `enrollmentTime` on iOS to match Android/Web
(ref: https://firebase.google.com/docs/reference/js/auth.multifactorinfo)

keep `enrollmentDate` around on ios for backwards compatibility, mark as
deprecated.

ref:
- https://github.com/invertase/react-native-firebase/blob/main/packages/auth/android/src/main/java/io/invertase/firebase/auth/ReactNativeFirebaseAuthModule.java#L2500
- https://github.com/invertase/react-native-firebase/blob/main/packages/auth/lib/index.d.ts#L483

split from invertase#7565

packages/auth/ios/RNFBAuth/RNFBAuthModule.m

@@ -1686,13 +1686,15 @@ - (NSDictionary *)firebaseUserToDict:(FIRUser *)user {
  NSMutableArray *enrolledFactors = [NSMutableArray array];
 
  for (FIRPhoneMultiFactorInfo *hint in hints) {
- NSString *enrollmentDate =
+ NSString *enrollmentTime =
  [[[NSISO8601DateFormatter alloc] init] stringFromDate:hint.enrollmentDate];
  [enrolledFactors addObject:@{
  @"uid" : hint.UID,
  @"factorId" : [self getJSFactorId:(hint.factorID)],
  @"displayName" : hint.displayName == nil ? [NSNull null] : hint.displayName,
- @"enrollmentDate" : enrollmentDate,
+ @"enrollmentTime" : enrollmentTime,
+ // @deprecated enrollmentDate kept for backwards compatibility, please use enrollmentTime
+ @"enrollmentDate" : enrollmentTime,
  }];
  }
  return enrolledFactors;
@@ -1745,4 +1747,4 @@ - (FIRActionCodeSettings *)buildActionCodeSettings:(NSDictionary *)actionCodeSet
  return settings;
 }
 
-@end
+@end