Revert the doc change done in r83880. str.replace with negative count value is not a feature.

Objects/bytesobject.c

@@ -2131,8 +2131,7 @@ PyDoc_STRVAR(replace__doc__,
 \n\
 Return a copy of B with all occurrences of subsection\n\
 old replaced by new.  If the optional argument count is\n\
-positive, only the first count occurrences are replaced. A\n\
-negative value of count replaces all occurrences");
+given, only first count occurances are replaced.");
 
 static PyObject *
 bytes_replace(PyBytesObject *self, PyObject *args)