[chore] remove check-legacy-docs from required status checks (#3644)

The check-legacy-docs workflow guards edits to the legacy `docs/` and
`i18n/zh-CN/docusaurus-plugin-content-docs/current/` trees, which are
being retired (dev moved to the docs-next plugin and the legacy plugin
runs with `includeCurrentVersion: false`). Drop it from the required
status checks on master *first*, so the follow-up PR that deletes the
workflow file does not leave every PR blocked waiting for a check that
no longer runs.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: morningman

.asf.yaml

@@ -53,7 +53,6 @@ github:
           - check-md-links
           - check-file-sizes
           - Build docs-next
-          - check-legacy-docs
   features:
     issues: true