[Security] Bump acorn from 6.1.0 to 6.4.1 Bumps [acorn](https://github.com/acornjs/acorn) from 6.1.0 to 6.4.1. **This update includes a security fix.** - [Release notes](https://github.com/acornjs/acorn/releases) - [Commits](https://github.com/acornjs/acorn/compare/6.1.0...6.4.1) Signed-off-by: dependabot-preview[bot]