Bump rust-toolchain from 1.88.0 to 1.91.1

Bumps [rust-toolchain](https://github.com/rust-lang/rust) from 1.88.0 to 1.91.1.
- [Release notes](https://github.com/rust-lang/rust/releases)
- [Changelog](https://github.com/rust-lang/rust/blob/main/RELEASES.md)
- [Commits](rust-lang/rust@1.88.0...1.91.1)

---
updated-dependencies:
- dependency-name: rust-toolchain
  dependency-version: 1.91.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

rust-toolchain.toml

@@ -1,5 +1,5 @@
 [toolchain]
-channel = "1.88.0"
+channel = "1.91.1"
 profile = "default" # see https://rust-lang.github.io/rustup/concepts/profiles.html
 components = [
   "rust-analyzer",