Remove mdlayher/raw dep

[Gobd]

https://github.com/mdlayher/raw is deprecated and easily replaced with https://github.com/mdlayher/packet

[pmazzini]

Related to #461

[codecov[bot]]

Codecov Report

Patch coverage: 66.66% and no project coverage change.

Comparison is base (974c6f0) 72.77% compared to head (df9ba4a) 72.77%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #499 +/- ## ======================================= Coverage 72.77% 72.77% ======================================= Files 90 90 Lines 5742 5742 ======================================= Hits 4179 4179 Misses 1391 1391 Partials 172 172 ``` | [Impacted Files](https://app.codecov.io/gh/insomniacslk/dhcp/pull/499?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=insomniac) | Coverage Δ | | |---|---|---| | [dhcpv4/nclient4/conn\_unix.go](https://app.codecov.io/gh/insomniacslk/dhcp/pull/499?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=insomniac#diff-ZGhjcHY0L25jbGllbnQ0L2Nvbm5fdW5peC5nbw==) | `62.33% <66.66%> (ø)` | |

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