feat(spec): stamp view-list-tabs-removed retiredAfter 17.4.0

The entry landed with #20357 after this branch's last merge. It is in no
published tarball, so it carries the package label (17.4.0, also npm latest).

Claude-Session: https://claude.ai/code/session_01ARcDurZ5j34RdqsGgc4jgH
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/spec/src/conversions/registry.ts

@@ -10863,6 +10863,7 @@ const viewListTabsRemoved: MetadataConversion = {
   id: 'view-list-tabs-removed',
   toMajor: 18,
   retiredFromLoadPath: true,
+  retiredAfter: '17.4.0',
   surface: 'view.list.tabs / view.listViews.*.tabs — the list view\'s own tab definitions',
   summary:
     "list-view key 'tabs' removed (ADR-0049 enforce-or-remove — parsed and stored, drawn by nothing: no "