Bump parcel from 2.15.2 to 2.15.4 in /src/Elastic.Documentation.Site

Bumps [parcel](https://github.com/parcel-bundler/parcel) from 2.15.2 to 2.15.4.
- [Release notes](https://github.com/parcel-bundler/parcel/releases)
- [Changelog](https://github.com/parcel-bundler/parcel/blob/v2/CHANGELOG.md)
- [Commits](https://github.com/parcel-bundler/parcel/commits)

---
updated-dependencies:
- dependency-name: parcel
  dependency-version: 2.15.4
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]