Issue #12164: Document (in docstring) that str.translate accepts None for the first argument.

Objects/stringobject.c

@@ -2173,7 +2173,9 @@ PyDoc_STRVAR(translate__doc__,
 Return a copy of the string S, where all characters occurring\n\
 in the optional argument deletechars are removed, and the\n\
 remaining characters have been mapped through the given\n\
-translation table, which must be a string of length 256.");
+translation table, which must be a string of length 256 or None.\n\
+If the table argument is None, no translation is applied and\n\
+the operation simply removes the characters in deletechars.");
 
 static PyObject *
 string_translate(PyStringObject *self, PyObject *args)