chore(deps): update which requirement from 7 to 8 (#807)

Updates the requirements on [which](https://github.com/harryfei/which-rs) to permit the latest version.
- [Release notes](https://github.com/harryfei/which-rs/releases)
- [Changelog](https://github.com/harryfei/which-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/harryfei/which-rs/compare/7.0.0...8.0.2)

---
updated-dependencies:
- dependency-name: which
  dependency-version: 8.0.2
  dependency-type: direct:production
...

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

crates/rmcp/Cargo.toml

@@ -82,7 +82,7 @@ tower-service = { version = "0.3", optional = true }
 process-wrap = { version = "9.0", features = ["tokio1"], optional = true }
 
 # for cross-platform executable path resolution
-which = { version = "7", optional = true }
+which = { version = "8", optional = true }
 
 # for ws transport
 # tokio-tungstenite ={ version = "0.26", optional = true }