go.mod: bump github.com/tailscale/peercred for Solaris

This pulls in Solaris/Illumos-specific:

  https://github.com/tailscale/peercred/pull/10
  https://go-review.googlesource.com/c/sys/+/639755

Updates tailscale/peercred#10 (from @nshalman)

Change-Id: I8211035fdcf84417009da352927149d68905c0f1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f