Bump handlebars from 4.2.1 to 4.4.0 in /build

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.2.1 to 4.4.0.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/wycats/handlebars.js/blob/v4.4.0/release-notes.md)
- [Commits](https://github.com/wycats/handlebars.js/compare/v4.2.1...v4.4.0

)

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