chore: remove some clippy lint allows

[ada4a]

Description

The FIXME says these lints should be fixed, but it looks like they already are, as no warnings appeared when I removed the allows. So I removed them for good.

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

This change doesn't cause any warnings on the libc-0.2 branch either, so:
@rustbot label +stable-nominated

[rustbot]

Error: Parsing relabel command in comment failed: a label delta when parsing: -nominated[!] (this cha

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