Bump acorn from 7.1.0 to 7.2.0

Bumps [acorn](https://github.com/acornjs/acorn) from 7.1.0 to 7.2.0.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@7.1.0...7.2.0)

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

Author: dependabot[bot]