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`Node.HomeDERP`, which superseded `LegacyDERPString` upstream at capver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.

hscontrol/mapper/tail_test.go

@@ -70,7 +70,6 @@ func TestTailNode(t *testing.T) {
 				Name:              "empty",
 				StableID:          "0",
 				HomeDERP:          0,
-				LegacyDERPString:  "127.3.3.40:0",
 				Hostinfo:          hiview(tailcfg.Hostinfo{}),
 				MachineAuthorized: true,
 
@@ -148,8 +147,7 @@ func TestTailNode(t *testing.T) {
 				PrimaryRoutes: []netip.Prefix{
 					netip.MustParsePrefix("192.168.0.0/24"),
 				},
-				HomeDERP:         0,
-				LegacyDERPString: "127.3.3.40:0",
+				HomeDERP: 0,
 				Hostinfo: hiview(tailcfg.Hostinfo{
 					RoutableIPs: []netip.Prefix{
 						tsaddr.AllIPv4(),
@@ -186,7 +184,6 @@ func TestTailNode(t *testing.T) {
 				Name:              "minimal.example.com.",
 				StableID:          "0",
 				HomeDERP:          0,
-				LegacyDERPString:  "127.3.3.40:0",
 				Hostinfo:          hiview(tailcfg.Hostinfo{}),
 				MachineAuthorized: true,