Bump acorn from 7.0.0 to 7.1.1 in /site (#4554)

Bumps [acorn](https://github.com/acornjs/acorn) from 7.0.0 to 7.1.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@7.0.0...7.1.1)

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

Author: dependabot[bot]