Bump markup5ever from 0.12.0 to 0.12.1 in /native/html5ever_nif (#146)

Bumps [markup5ever](https://github.com/servo/html5ever) from 0.12.0 to 0.12.1.
- [Commits](servo/html5ever@markup5ever-v0.12.0...markup5ever-v0.12.1)

---
updated-dependencies:
- dependency-name: markup5ever
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]