Bump braces and gulp in /src/main/content/antora_ui

Bumps [braces](https://github.com/micromatch/braces) to 3.0.3 and updates ancestor dependency [gulp](https://github.com/gulpjs/gulp). These dependencies need to be updated together.


Updates `braces` from 3.0.2 to 3.0.3
- [Changelog](https://github.com/micromatch/braces/blob/master/CHANGELOG.md)
- [Commits](micromatch/braces@3.0.2...3.0.3)

Updates `gulp` from 4.0.2 to 5.0.0
- [Release notes](https://github.com/gulpjs/gulp/releases)
- [Changelog](https://github.com/gulpjs/gulp/blob/master/CHANGELOG.md)
- [Commits](gulpjs/gulp@v4.0.2...v5.0.0)

---
updated-dependencies:
- dependency-name: braces
  dependency-type: indirect
- dependency-name: gulp
  dependency-type: direct:development
...

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