go.mod: update to github.com/tailscale/netlink library that doesn't require vishvananda/netlink

After the upstream PR is merged, we can point directly at github.com/vishvananda/netlink
and retire github.com/tailscale/netlink.

See https://github.com/vishvananda/netlink/pull/1006

Updates #12298

Signed-off-by: Percy Wegmann <percy@tailscale.com>

cmd/tailscale/depaware.txt

@@ -60,10 +60,10 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         github.com/tailscale/goupnp/soap                             from github.com/tailscale/goupnp+
         github.com/tailscale/goupnp/ssdp                             from github.com/tailscale/goupnp
    L 💣 github.com/tailscale/netlink                                 from tailscale.com/util/linuxfw
+   L 💣 github.com/tailscale/netlink/nl                              from github.com/tailscale/netlink
         github.com/tailscale/web-client-prebuilt                     from tailscale.com/client/web
         github.com/tcnksm/go-httpstat                                from tailscale.com/net/netcheck
         github.com/toqueteos/webbrowser                              from tailscale.com/cmd/tailscale/cli
-   L 💣 github.com/vishvananda/netlink/nl                            from github.com/tailscale/netlink
    L    github.com/vishvananda/netns                                 from github.com/tailscale/netlink+
         github.com/x448/float16                                      from github.com/fxamacker/cbor/v2
      💣 go4.org/mem                                                  from tailscale.com/client/tailscale+