Bump indexmap from 2.13.0 to 2.13.1 in /autorust (#768)

Bumps [indexmap](https://github.com/indexmap-rs/indexmap) from 2.13.0 to 2.13.1.
- [Changelog](https://github.com/indexmap-rs/indexmap/blob/main/RELEASES.md)
- [Commits](indexmap-rs/indexmap@2.13.0...2.13.1)

---
updated-dependencies:
- dependency-name: indexmap
  dependency-version: 2.13.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]