buffer: remove unreachable overflow check in atob

Author: haramj

lib/buffer.js

@@ -1302,8 +1302,6 @@ function atob(input) {
       throw lazyDOMException(
         'The string to be decoded is not correctly encoded.',
         'InvalidCharacterError');
-    case -3: // Possible overflow
-      throw new ERR_INVALID_ARG_VALUE('input', result, 'The string to be decoded is too long.');
     default:
       return result;
   }