Use later stable rust version 1.81.0 to fix the CI

[musaprg]

This PR bumps the rust toolchain version to 1.81.0 to pass the CI failing due to the following error.

error: failed to compile `cross v0.2.5 (https://github.com/cross-rs/cross#4090beca)`, intermediate artifacts can be found at `/tmp/cargo-installPBmzPf`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.

Caused by:
  rustc 1.80.0 is not supported by the following package:
    [email protected] requires rustc 1.81
  Either upgrade rustc or select compatible dependency versions with
  `cargo update <name>@<current-ver> --precise <compatible-ver>`
  where `<compatible-ver>` is the latest version supporting rustc 1.80.0

I've briefly checked the compatibility notes section of the release note, but I don't think bumping up the version would affect the youki's code base.

https://releases.rs/docs/1.81.0/#compatibility-notes

[musaprg]

The latest stable version appears to be 1.83.0, but I'm not sure if we could bump the dependent version over three minor versions forward instead of bumping a single minor version. What are your thoughts on that?

[utam0k]

Thanks!

[utam0k]

What are your thoughts on that?

We don't have a rule about that, but this PR is worth it.