bpo-32720: Fixed the replacement field grammar documentation. (GH-5544) (GH-5546)

`arg_name` and `element_index` are defined as `digit`+ instead of `integer`.
(cherry picked from commit 7a561afd2c79f63a6008843b83733911d07f0119)

Co-authored-by: Mariatta <Mariatta@users.noreply.github.com>
1 file changed