Bump fast-xml-parser and @springio/antora-extensions in /antora

Bumps [fast-xml-parser](https://github.com/NaturalIntelligence/fast-xml-parser) to 5.5.7 and updates ancestor dependency [@springio/antora-extensions](https://github.com/spring-io/antora-extensions). These dependencies need to be updated together.

Updates `fast-xml-parser` from 4.5.4 to 5.5.7
- [Release notes](https://github.com/NaturalIntelligence/fast-xml-parser/releases)
- [Changelog](https://github.com/NaturalIntelligence/fast-xml-parser/blob/master/CHANGELOG.md)
- [Commits](NaturalIntelligence/fast-xml-parser@v4.5.4...v5.5.7)

Updates `@springio/antora-extensions` from 1.14.7 to 1.14.9
- [Changelog](https://github.com/spring-io/antora-extensions/blob/main/CHANGELOG.adoc)
- [Commits](spring-io/antora-extensions@v1.14.7...v1.14.9)

---
updated-dependencies:
- dependency-name: fast-xml-parser
  dependency-version: 5.5.7
  dependency-type: indirect
- dependency-name: "@springio/antora-extensions"
  dependency-version: 1.14.9
  dependency-type: direct:production
...

See gh-49671

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Author: dependabot[bot]