deps: Accept unmaintained crate for now (#2918)

## Description

This crate is unmaintained, but used indirectly by some dependencies.
No big deal.

## Breaking Changes

<!-- Optional, if there are any breaking changes document them,
including how to migrate older code. -->

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR.
-->

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

deny.toml

@@ -34,6 +34,7 @@ license-files = [
 [advisories]
 ignore = [
       "RUSTSEC-2024-0370", # unmaintained, no upgrade available
+      "RUSTSEC-2024-0384", # unmaintained, no upgrade available
 ]
 
 [sources]