housekeeping: bump handlebars from 4.0.11 to 4.1.2 (via #1440)

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.0.11 to 4.1.2.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/wycats/handlebars.js/blob/master/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.0.11...v4.1.2)

Signed-off-by: dependabot[bot] <support@github.com>