Update tun requirement from 0.7 to 0.8

Updates the requirements on [tun](https://github.com/meh/rust-tun) to permit the latest version.
- [Release notes](https://github.com/meh/rust-tun/releases)
- [Commits](https://github.com/meh/rust-tun/compare/v0.7.0...v0.8.0)

---
updated-dependencies:
- dependency-name: tun
  dependency-version: 0.8.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -50,7 +50,7 @@ thiserror = "2"
 tokio = { version = "1", features = ["full"] }
 tokio-util = "0.7"
 tproxy-config = { version = "6", default-features = false }
-tun = { version = "0.7", features = ["async"] }
+tun = { version = "0.8", features = ["async"] }
 udp-stream = { version = "0.0.12", default-features = false }
 unicase = "2"
 url = "2"