Clarify that D417 only checks docstrings with an arguments section

[MichaReiser]

Summary

This came up in #16477

It's not obvious from the D417 rule's documentation that it only checks docstrings
with an arguments section. Functions without such a section aren't checked.

This PR tries to make this clearer in the documentation.

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check encountered linter errors. (no lint changes; 2 project errors)

RasaHQ/rasa (error)

Failed to clone RasaHQ/rasa: error: RPC failed; curl 92 HTTP/2 stream 5 was not closed cleanly: CANCEL (err 8)
error: 2876 bytes of body are still expected
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output

zulip/zulip (error)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --no-preview --select ALL

Failed to clone zulip/zulip: error: RPC failed; curl 92 HTTP/2 stream 5 was not closed cleanly: CANCEL (err 8)
error: 4078 bytes of body are still expected
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output

Linter (preview)

✅ ecosystem check detected no linter changes.

[ntBre]

I added one comment, but thanks for doing this!

[ntBre]

This line looks like it might have gotten cut off somehow. And did you want to remove the note about the google convention? It is mentioned earlier in the docs, but this seems to add a little more clarification.

I think the change on 1170 might be enough here. (actually I slightly prefer line 1172, but either of those on line 1170 would be great)

I can't add a suggestion on deleted lines, but my suggestion is:

/// Note that this rule only checks docstrings with an arguments (e.g. `Args`) section.
///
/// This rule is enabled when using the `google` convention, and disabled when
/// using the `pep257` and `numpy` conventions.

[MichaReiser]

And did you want to remove the note about the google convention?

Definitely not. Thanks for catching this!