PEP 634: Fix error typo in mapping patterns (TypeError ->ValueError) (GH-1839)

pep-0634.rst

@@ -412,7 +412,7 @@ and it must be last.
 A mapping pattern may not contain duplicate key values.
 (If all key patterns are literal patterns this is considered a
 syntax error; otherwise this is a runtime error and will
-raise ``TypeError``.)
+raise ``ValueError``.)
 
 A mapping pattern fails if the subject value is not an instance of
 ``collections.abc.Mapping``.