fix(deps): update rust crate tun2 to v3.1.8

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
tun2	dependencies	patch	3.1.7 -> 3.1.8

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Release Notes

ssrlive/rust-tun (tun2)

### [`v3.1.8`](https://redirect.github.com/tun2proxy/rust-tun/releases/tag/v3.1.8) [Compare Source](https://redirect.github.com/ssrlive/rust-tun/compare/v3.1.7...v3.1.8) **Full Changelog**: https://github.com/tun2proxy/rust-tun/compare/v3.1.7...v3.1.8

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