Bump rescript from 12.0.0-beta.5 to 12.0.0-beta.6

Bumps [rescript](https://github.com/rescript-lang/rescript-compiler) from 12.0.0-beta.5 to 12.0.0-beta.6.
- [Release notes](https://github.com/rescript-lang/rescript-compiler/releases)
- [Changelog](https://github.com/rescript-lang/rescript/blob/master/CHANGELOG.md)
- [Commits](rescript-lang/rescript@v12.0.0-beta.5...v12.0.0-beta.6)

---
updated-dependencies:
- dependency-name: rescript
  dependency-version: 12.0.0-beta.6
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]