Bump bitvec from 0.19.5 to 0.19.6

Bumps [bitvec](https://github.com/myrrlyn/bitvec) from 0.19.5 to 0.19.6.
- [Release notes](https://github.com/myrrlyn/bitvec/releases)
- [Changelog](https://github.com/bitvecto-rs/bitvec/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/myrrlyn/bitvec/commits)

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

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