all: update golang.zx2c4.com/wireguard to github.com/tailscale/wireguard-go (#6692)

This is temporary while we work to upstream performance work in
https://github.com/WireGuard/wireguard-go/pull/64. A replace directive
is less ideal as it breaks dependent code without duplication of the
directive.

Signed-off-by: Jordan Whited <jordan@tailscale.com>

net/tstun/linkattrs_linux.go

@@ -7,8 +7,8 @@ package tstun
 import (
 	"github.com/mdlayher/genetlink"
 	"github.com/mdlayher/netlink"
+	"github.com/tailscale/wireguard-go/tun"
 	"golang.org/x/sys/unix"
-	"golang.zx2c4.com/wireguard/tun"
 )
 
 // setLinkSpeed sets the advertised link speed of the TUN interface.