Fixed OTP text entry on iOS (thanks @pipiwoaini!)

Fixes #13717

Author: slouken

src/video/uikit/SDL_uikitviewcontroller.m

@@ -575,6 +575,10 @@ - (void)keyboardDidHide:(NSNotification *)notification
 - (void)textFieldTextDidChange:(NSNotification *)notification
 {
     if (textField.markedTextRange == nil) {
+        if (isOTPMode && labs((NSInteger)textField.text.length - (NSInteger)committedText.length) != 1) {
+            return;
+        }
+
         NSUInteger compareLength = SDL_min(textField.text.length, committedText.length);
         NSUInteger matchLength;