Update somewhat incorrect comment.

Cython/Utility/FunctionArguments.c

@@ -280,7 +280,7 @@ static int __Pyx_ParseOptionalKeywords(
                 #if !CYTHON_COMPILING_IN_PYPY && PY_MAJOR_VERSION >= 3
                     (__Pyx_PyUnicode_GET_LENGTH(**name) != __Pyx_PyUnicode_GET_LENGTH(key)) ? 1 :
                 #endif
-                    // need to convert argument name from bytes to unicode for comparison
+                    // In Py2, we may need to convert the argument name from str to unicode for comparison.
                     PyUnicode_Compare(**name, key);
                 if (cmp < 0 && unlikely(PyErr_Occurred())) goto bad;
                 if (cmp == 0) {