chore(deps): bump rust-toolchain from 1.90.0 to 1.91.0 (#55)

Bumps [rust-toolchain](https://github.com/rust-lang/rust) from 1.90.0 to 1.91.0.
- [Release notes](https://github.com/rust-lang/rust/releases)
- [Changelog](https://github.com/rust-lang/rust/blob/master/RELEASES.md)
- [Commits](rust-lang/rust@1.90.0...1.91.0)

---
updated-dependencies:
- dependency-name: rust-toolchain
  dependency-version: 1.91.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

rust-toolchain.toml

@@ -1,2 +1,2 @@
 [toolchain]
-channel = "1.90.0"
+channel = "1.91.0"