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

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