build: Bump async-signal from 0.2.5 to 0.2.6

Bumps [async-signal](https://github.com/smol-rs/async-signal) from 0.2.5 to 0.2.6.
- [Release notes](https://github.com/smol-rs/async-signal/releases)
- [Changelog](https://github.com/smol-rs/async-signal/blob/master/CHANGELOG.md)
- [Commits](smol-rs/async-signal@v0.2.5...v0.2.6)

---
updated-dependencies:
- dependency-name: async-signal
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>