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`Node.HomeDERP`, which superseded `LegacyDERPString` upstream at capver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/capver/capver_test_data.go

@@ -9,10 +9,9 @@ var tailscaleLatestMajorMinorTests = []struct {
 	stripV   bool
 	expected []string
 }{
-	{3, false, []string{"v1.92", "v1.94", "v1.96"}},
-	{2, true, []string{"1.94", "1.96"}},
+	{3, false, []string{"v1.94", "v1.96", "v1.98"}},
+	{2, true, []string{"1.96", "1.98"}},
 	{10, true, []string{
-		"1.78",
 		"1.80",
 		"1.82",
 		"1.84",
@@ -22,6 +21,7 @@ var tailscaleLatestMajorMinorTests = []struct {
 		"1.92",
 		"1.94",
 		"1.96",
+		"1.98",
 	}},
 	{0, false, nil},
 }
@@ -30,7 +30,7 @@ var capVerMinimumTailscaleVersionTests = []struct {
 	input    tailcfg.CapabilityVersion
 	expected string
 }{
-	{109, "v1.78"},
+	{113, "v1.80"},
 	{32, "v1.24"},
 	{41, "v1.30"},
 	{46, "v1.32"},