Pin to the older msrv version.

[evshary]

Fix the CI failure
https://github.com/eclipse-uprotocol/up-transport-zenoh-rust/actions/runs/11265771929/job/31328151458

If we use msrv 0.16.x, it needs at least Rust 1.78.0. I guess it will be good to support the minimum version we need.
Therefore, I decide to fix at 0.15.1.

[sophokles73]

IMHO the issue is that you are explicitly setting the rust toolchain to 1.75 using the rust-toolchain.yaml file.
FMPOV this is not really necessary. The msrv check in the nightly build is specifically designed to make sure that your code can actually be compiled using rust 1.75 ...
If you remove the rust-toolchain.yaml file, everthing should work as expected. Alternatively, you could explicitly switch to the stable toolchain before invoking cargo install msrv-check ...

[evshary]

IMHO the issue is that you are explicitly setting the rust toolchain to 1.75 using the rust-toolchain.yaml file. FMPOV this is not really necessary. The msrv check in the nightly build is specifically designed to make sure that your code can actually be compiled using rust 1.75 ... If you remove the rust-toolchain.yaml file, everthing should work as expected. Alternatively, you could explicitly switch to the stable toolchain before invoking cargo install msrv-check ...

I remember the reason I added rust-toolchain.yaml is because Zenoh couldn't compile with the latest compiler at that time. Since this is not the case, I agree it's fine to remove it now.

[sophokles73]

LGTM