Remove redundant type check.

Cython/Utility/FunctionArguments.c

@@ -211,7 +211,7 @@ static int __Pyx_ParseOptionalKeywords(
 
         name = first_kw_arg;
         #if PY_MAJOR_VERSION < 3
-        if (likely(PyString_CheckExact(key)) || likely(PyString_Check(key))) {
+        if (likely(PyString_Check(key))) {
             while (*name) {
                 if ((CYTHON_COMPILING_IN_PYPY || PyString_GET_SIZE(**name) == PyString_GET_SIZE(key))
                         && _PyString_Eq(**name, key)) {