build(deps): bump chacha20 from 0.9.0 to 0.9.1 (#522)

Bumps [chacha20](https://github.com/RustCrypto/stream-ciphers) from 0.9.0 to 0.9.1.
- [Release notes](https://github.com/RustCrypto/stream-ciphers/releases)
- [Commits](RustCrypto/stream-ciphers@chacha20-v0.9.0...chacha20-v0.9.1)

---
updated-dependencies:
- dependency-name: chacha20
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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