Update to 6.8.3

• Update to 6.8.3
• Switch to the Darwin distribution instead of the Linux one since files like node_modules/x-pack/plugins/reporting/server/browsers/chromium/paths.js have platform specifications and in the Darwin distribution that includes FreeBSD (not so for the Linux one).
• Depend on node 10, which is the version distributed with 6.8.3
• Improve pkg-deinstall by indicating how to permanently delete data

PR: 240694
Approved by: maintainer timeout
Sponsored by: The FreeBSD Foundation