Bump antora from 3.2.0-alpha.8 to 3.2.0-alpha.9 in /docs

Bumps [antora](https://gitlab.com/antora/antora) from 3.2.0-alpha.8 to 3.2.0-alpha.9.
- [Changelog](https://gitlab.com/antora/antora/blob/main/CHANGELOG.adoc)
- [Commits](https://gitlab.com/antora/antora/compare/v3.2.0-alpha.8...v3.2.0-alpha.9)

---
updated-dependencies:
- dependency-name: antora
  dependency-version: 3.2.0-alpha.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/package.json

@@ -1,6 +1,6 @@
 {
   "dependencies": {
-    "antora": "3.2.0-alpha.8",
+    "antora": "3.2.0-alpha.9",
     "@antora/atlas-extension": "1.0.0-alpha.2",
     "@antora/collector-extension": "1.0.1",
     "@asciidoctor/tabs": "1.0.0-beta.6",