Bump activesupport, middleman and govuk_schemas

Bumps [activesupport](https://github.com/rails/rails), [middleman](https://github.com/middleman/middleman) and [govuk_schemas](https://github.com/alphagov/govuk_schemas_gem). These dependencies needed to be updated together.

Updates `activesupport` from 7.0.8.7 to 8.0.2
- [Release notes](https://github.com/rails/rails/releases)
- [Changelog](https://github.com/rails/rails/blob/v8.0.2/activesupport/CHANGELOG.md)
- [Commits](rails/rails@v7.0.8.7...v8.0.2)

Updates `middleman` from 4.5.0 to 4.6.0
- [Changelog](https://github.com/middleman/middleman/blob/main/CHANGELOG.md)
- [Commits](middleman/middleman@v4.5.0...v4.6.0)

Updates `govuk_schemas` from 5.0.2 to 6.0.0
- [Changelog](https://github.com/alphagov/govuk_schemas/blob/main/CHANGELOG.md)
- [Commits](alphagov/govuk_schemas@v5.0.2...v6.0.0)

---
updated-dependencies:
- dependency-name: activesupport
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: middleman
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: govuk_schemas
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]