Issue #16495: remove extraneous NULL encoding check from bytes_decode().

The NULL encoding check in bytes_decode() was unnecessary because this case
is already taken care of by the call to _Py_normalize_encoding() inside
PyUnicode_Decode().

Objects/bytesobject.c

@@ -2236,8 +2236,6 @@ bytes_decode(PyObject *self, PyObject *args, PyObject *kwargs)
 
     if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|ss:decode", kwlist, &encoding, &errors))
         return NULL;
-    if (encoding == NULL)
-        encoding = PyUnicode_GetDefaultEncoding();
     return PyUnicode_FromEncodedObject(self, encoding, errors);
 }