[`ruff`] Stabilize `unnecessary-nested-literal` (`RUF041`) (#16648)
Summary
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Stabilizes RUF041. The tests are already in the right place, and the
docs look good.
Test Plan
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0 issues, 1 [PR] fixing nested literals and unions the day after the
rule was added. No changes since then
I wonder if the fix in that PR could be relevant for
https://github.com/astral-sh/ruff/pull/16639, where I noticed a
potential issue with `Union`. It could be unrelated, though.
[PR]: https://github.com/astral-sh/ruff/pull/14641