Fix whitespace

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Author: JanEricNitschke

src/typing_extensions.py

@@ -2637,7 +2637,7 @@ def _typevartuple_prepare_subst(alias, args):
 
             def __mro_entries__(bases):
                 raise TypeError("Cannot subclass an instance of TypeVarTuple.")
-            tvt.__mro_entries__ =  __mro_entries__
+            tvt.__mro_entries__ = __mro_entries__
 
             return tvt