Remove remaining :rtype:s from docstrings

[akx]

The type annotations for the functions describe the return type anyway, so no great reason I can think of to keep a redundant other copy around.

Noticed these in Chops while working on #9738 and figured I'd do a full sweep.

[codspeed-hq]

Merging this PR will not alter performance

✅ 331 untouched benchmarks

---

_{Comparing akx:remove-rtypes (5ad6072) with main (6590b1b)}

[akx]

How did the main commit fc7cec1 end up with @hugovk's authorship 😮

Or rather, I think squash merging PRs has retained the PR author's credits in the past? 🤔

[hugovk]

It's not a squash merge commit, it's a regular merge commit.

fc7cec1 is my merge and it has two parents, one of which is your commit 5ad6072.

[akx]

Ah! Sorry for the noise, my bad. I didn't check the parents correctly. Thanks!