Update mdlayher/vsock to v1.2.1

[rillian]

Dependency bumps. Also updates mdlayher/socket to v0.4.1.

This is a manual version of #16 to check if the persistent ci failures there are a glitch.

[rillian]

Nope, the failure is repeatable

Running [/home/runner/golangci-lint-1.58.0-linux-amd64/golangci-lint run --out-format=github-actions] in [] ...
level=warning msg="[runner] Can't run linter goanalysis_metalinter: buildir: failed to load package socket: could not load export data: no export data for "github.com/mdlayher/socket""
level=error msg="Running error: can't run linter goanalysis_metalinter\nbuildir: failed to load package socket: could not load export data: no export data for "github.com/mdlayher/socket""