Bump rand from 0.7.2 to 0.8.6

Bumps [rand](https://github.com/rust-random/rand) from 0.7.2 to 0.8.6.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/0.8.6/CHANGELOG.md)
- [Commits](rust-random/rand@0.7.2...0.8.6)

---
updated-dependencies:
- dependency-name: rand
  dependency-version: 0.8.6
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]