- Use default github rust version
- Stop using clippy action, it has been unmaintained since 2020
- No longer enforce nightly fmt rules in CI (they can still be enforced
  in commit hooks or nix
- No longer use cargo test unstable options
- Run `cargo clippy --fix` to fix new errors

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 20 to 21.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v20...v21)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 18 to 20.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v18...v20)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

* update nix to flake

* add nix sanity check cronjob

Bumps [Swatinem/rust-cache](https://github.com/Swatinem/rust-cache) from 1 to 2.
- [Release notes](https://github.com/Swatinem/rust-cache/releases)
- [Changelog](https://github.com/Swatinem/rust-cache/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Swatinem/rust-cache/compare/v1...v2)

---
updated-dependencies:
- dependency-name: Swatinem/rust-cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Bumps [styfle/cancel-workflow-action](https://github.com/styfle/cancel-workflow-action) from 0.9.1 to 0.11.0.
- [Release notes](https://github.com/styfle/cancel-workflow-action/releases)
- [Commits](https://github.com/styfle/cancel-workflow-action/compare/0.9.1...0.11.0)

---
updated-dependencies:
- dependency-name: styfle/cancel-workflow-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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