Bump @springio/antora-xref-extension in /antora

Bumps [@springio/antora-xref-extension](https://github.com/spring-io/antora-xref-extension) from 1.0.0-alpha.4 to 1.0.0-alpha.5.
- [Changelog](https://github.com/spring-io/antora-xref-extension/blob/main/CHANGELOG.adoc)
- [Commits](spring-io/antora-xref-extension@v1.0.0-alpha.4...v1.0.0-alpha.5)

---
updated-dependencies:
- dependency-name: "@springio/antora-xref-extension"
  dependency-version: 1.0.0-alpha.5
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

antora/package-lock.json

@@ -8,7 +8,7 @@
     "@antora/site-generator": "3.2.0-alpha.4",
     "@antora/atlas-extension": "1.0.0-alpha.5",
     "@springio/antora-extensions": "1.14.7",
-    "@springio/antora-xref-extension": "1.0.0-alpha.4",
+    "@springio/antora-xref-extension": "1.0.0-alpha.5",
     "@springio/antora-zip-contents-collector-extension": "1.0.0-alpha.8",
     "@asciidoctor/tabs": "1.0.0-beta.6",
     "@springio/asciidoctor-extensions": "1.0.0-alpha.17",