chore: revert AGENTS.md to simple link to CLAUDE.md

CLAUDE.md already contains the Upgrading section, no need to
duplicate in AGENTS.md.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AGENTS.md

@@ -2,8 +2,4 @@
 
 This file provides guidance for AI coding agents when working with code in this repository.
 
-For full project guidance, see [CLAUDE.md](./CLAUDE.md).
-
-## Upgrading
-
-To upgrade this project to the latest Ant Design Pro version, follow the instructions in [.claude/skills/pro-upgrade/SKILL.md](./.claude/skills/pro-upgrade/SKILL.md).
+For full project guidance, see [CLAUDE.md](./CLAUDE.md).