Update `lru` to >=0.16.3

[rkrishn7]

cargo deny reports an unsound advisory with the current version of lru:

    ├ ID: RUSTSEC-2026-0002
    ├ Advisory: https://rustsec.org/advisories/RUSTSEC-2026-0002
    ├ Affected versions of this crate contain a soundness issue in the `IterMut`
      iterator implementation. The `IterMut::next` and `IterMut::next_back`
      methods temporarily create an exclusive reference to the key when
      dereferencing the internal node pointer.
      
      This invalidates the shared pointer held by the internal `HashMap`,
      violating Stacked Borrows rules.

[lucieleblanc]

Will there be a new release that includes #2799? I'm happy to see it was merged, and it'd be great to have an official release containing the fix so downstream dependencies can update to include it.

[fulmicoton]

I think @PSeitz is planning an imminent release.