go.mod: bump github.com/go4org/hashtriemap for slight speed boost

(bumping in oss mostly to get it into corp, and we require them to be in sync
for now. But we do use this in derpserver too.)

Updates tailscale/corp#46884

Change-Id: If01e3e91787e9ec4331eb9c997292239c6b379f1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>