build(deps): bump activesupport from 5.2.2 to 6.0.3.1 in /docs

Bumps [activesupport](https://github.com/rails/rails) from 5.2.2 to 6.0.3.1.
- [Release notes](https://github.com/rails/rails/releases)
- [Changelog](https://github.com/rails/rails/blob/v6.0.3.1/activesupport/CHANGELOG.md)
- [Commits](rails/rails@v5.2.2...v6.0.3.1)

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