fix: bump coder/tailscale to pick up RTM_MISS fix (#24187)

## What

Bumps `coder/tailscale` to
[`e956a95`](https://github.com/coder/tailscale/commit/e956a950740bd737c55451f56e77038f7430a919)
([PR #113](https://github.com/coder/tailscale/pull/113)) to pick up the
`RTM_MISS` fix for the Darwin network monitor.

Already released on `release/2.31` as v2.31.8. (#24185) to unblock a
customer. This PR is to update `main`.

## Why

On Darwin, `RTM_MISS` route-socket messages (fired on every failed route
lookup) were not filtered by `netmon`, causing each one to be treated as
a `LinkChange`. When netcheck sends STUN probes to an IPv6 address with
no route, this creates a self-sustaining feedback loop: `RTM_MISS` →
`LinkChange` → `ReSTUN` → netcheck → v6 STUN probe → `RTM_MISS` → …

The loop drives DERP home-region flapping at ~70× baseline, which at
fleet scale saturates PostgreSQL's `NOTIFY` lock and causes coordinator
health-check timeouts.

The upstream fix adds a single `if msg.Type == unix.RTM_MISS { return
true }` check to `skipRouteMessage`. This is safe because `RTM_MISS` is
a lookup-path signal, not a table-mutation signal — route withdrawals
always emit `RTM_DELETE` before any subsequent lookup can miss.

Of note is that this issue has only been reported recently, since users
updated to macOS 26.4.

Relates to ENG-2394

go.mod

@@ -36,7 +36,7 @@ replace github.com/tcnksm/go-httpstat => github.com/coder/go-httpstat v0.0.0-202
 
 // There are a few minor changes we make to Tailscale that we're slowly upstreaming. Compare here:
 // https://github.com/tailscale/tailscale/compare/main...coder:tailscale:main
-replace tailscale.com => github.com/coder/tailscale v1.1.1-0.20260313130012-33e050fd4bd9
+replace tailscale.com => github.com/coder/tailscale v1.1.1-0.20260409064601-e956a950740b
 
 // This is replaced to include
 // 1. a fix for a data race: c.f. https://github.com/tailscale/wireguard-go/pull/25

go.sum

@@ -350,8 +350,8 @@ github.com/coder/serpent v0.14.0 h1:g7vt2zBMp3nWyAvyhvQduaI53Ku65U3wITMi01+/8pU=
 github.com/coder/serpent v0.14.0/go.mod h1:7OIvFBYMd+OqarMy5einBl8AtRr8LliopVU7pyrwucY=
 github.com/coder/ssh v0.0.0-20231128192721-70855dedb788 h1:YoUSJ19E8AtuUFVYBpXuOD6a/zVP3rcxezNsoDseTUw=
 github.com/coder/ssh v0.0.0-20231128192721-70855dedb788/go.mod h1:aGQbuCLyhRLMzZF067xc84Lh7JDs1FKwCmF1Crl9dxQ=
-github.com/coder/tailscale v1.1.1-0.20260313130012-33e050fd4bd9 h1:y9SeiKzMyyip1eQpBtcdH4StMQgnli1Ymy8Uecrqn7U=
-github.com/coder/tailscale v1.1.1-0.20260313130012-33e050fd4bd9/go.mod h1:q+R4UL4pPb0CpaSNVUTDsg0kZeL/OlqjRNO9XbJxU5g=
+github.com/coder/tailscale v1.1.1-0.20260409064601-e956a950740b h1:HW3db+iEczHHSsPLJokZRJTO788qf782qJcR9YAeAaM=
+github.com/coder/tailscale v1.1.1-0.20260409064601-e956a950740b/go.mod h1:9lK5yqqKpK5yhDv4G8ZDDHr2S8EATEjLyUkLTKDbPzU=
 github.com/coder/terraform-config-inspect v0.0.0-20250107175719-6d06d90c630e h1:JNLPDi2P73laR1oAclY6jWzAbucf70ASAvf5mh2cME0=
 github.com/coder/terraform-config-inspect v0.0.0-20250107175719-6d06d90c630e/go.mod h1:Gz/z9Hbn+4KSp8A2FBtNszfLSdT2Tn/uAKGuVqqWmDI=
 github.com/coder/terraform-provider-coder/v2 v2.15.0 h1:sdKV3JvwlL7FNuSfaba0pm2WsPTBG7d0H6lmbzX+q4M=