Discourse core is switching to pnpm for JS package management

[david (David Taylor)]

Thanks @Architect. These PRs will suppress the upgrade messages:

• UX: Suppress pnpm upgrade notifications in build logs by davidtaylorhq · Pull Request #240 · discourse/docker_manager · GitHub

• Suppress pnpm upgrade notices in logs by davidtaylorhq · Pull Request #866 · discourse/discourse_docker · GitHub