Bump handlebars from 4.7.6 to 4.7.7 (#6717)

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.7.6 to 4.7.7.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/handlebars-lang/handlebars.js/blob/master/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.7.6...v4.7.7)

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