Update thiserror requirement in /crates/mux-client-error

Updates the requirements on [thiserror](https://github.com/dtolnay/thiserror) to permit the latest version.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.29...2.0.0)

---
updated-dependencies:
- dependency-name: thiserror
  dependency-type: direct:production
...

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

crates/mux-client-error/Cargo.toml

@@ -13,5 +13,5 @@ keywords = ["ssh", "openssh", "multiplex", "async", "network"]
 categories = ["asynchronous", "network-programming", "api-bindings"]
 
 [dependencies]
-thiserror = "1.0.29"
+thiserror = "2.0.0"
 ssh_format_error = "0.1"