capver, types: bump to tailscale v1.98, drop LegacyDERPString

Regenerate capver for tailscale v1.98 — `MinSupportedCapabilityVersion`
slides 109 → 113 (v1.78 → v1.80). v1.80+ clients understand
`Node.HomeDERP`, which superseded `LegacyDERPString` upstream at capver
111. Drops the emit, plumbing, the trip-wire that caught this cleanup,
the golden test fixtures, and the integration check on
`peer.LegacyDERPString()` — the sibling `HomeDERP` check covers intent.

`v1.98` was added by hand to `capver_generated.go` because tailscale
skipped publishing v1.97/v1.98 to ghcr until late in the cycle; a clean
regeneration produces the same content.

integration/helpers.go

@@ -791,7 +791,6 @@ func assertValidNetmap(t *testing.T, client TailscaleClient) {
 		assert.Falsef(c, netmap.SelfNode.DiscoKey().IsZero(), "%q does not have a valid DiscoKey", client.Hostname())
 
 		for _, peer := range netmap.Peers {
-			assert.NotEqualf(c, "127.3.3.40:0", peer.LegacyDERPString(), "peer (%s) has no home DERP in %q's netmap, got: %s", peer.ComputedName(), client.Hostname(), peer.LegacyDERPString()) //nolint:staticcheck // SA1019: testing legacy field
 			assert.NotEqualf(c, 0, peer.HomeDERP(), "peer (%s) has no home DERP in %q's netmap, got: %d", peer.ComputedName(), client.Hostname(), peer.HomeDERP())
 
 			assert.Truef(c, peer.Hostinfo().Valid(), "peer (%s) of %q does not have Hostinfo", peer.ComputedName(), client.Hostname())