Allow Generic OAuth for Facebook and Apple when using the auth emulator. (#6702)

FirebaseAuth/Sources/AuthProvider/OAuth/FIROAuthProvider.m

@@ -203,12 +203,14 @@ static NSString *const kCustomUrlSchemePrefix = @"app-";
     @return An Instance of @c FIROAuthProvider.
   */
 - (nullable instancetype)initWithProviderID:(NSString *)providerID auth:(FIRAuth *)auth {
-  NSAssert(![providerID isEqual:FIRFacebookAuthProviderID],
-           @"Sign in with Facebook is not supported via generic IDP; the Facebook TOS "
-            "dictate that you must use the Facebook iOS SDK for Facebook login.");
-  NSAssert(![providerID isEqual:@"apple.com"],
-           @"Sign in with Apple is not supported via generic IDP; You must use the Apple iOS SDK"
-            " for Sign in with Apple.");
+  if (!auth.requestConfiguration.emulatorHostAndPort) {
+    NSAssert(![providerID isEqual:FIRFacebookAuthProviderID],
+             @"Sign in with Facebook is not supported via generic IDP; the Facebook TOS "
+              "dictate that you must use the Facebook iOS SDK for Facebook login.");
+    NSAssert(![providerID isEqual:@"apple.com"],
+             @"Sign in with Apple is not supported via generic IDP; You must use the Apple iOS SDK"
+              " for Sign in with Apple.");
+  }
   self = [super init];
   if (self) {
     _auth = auth;