www/node: Update 12.8.0 -> 12.8.1

This is a security release. All Node.js users should consult the security
release summary at
https://nodejs.org/en/blog/vulnerability/aug-2019-security-releases/
for details on patched vulnerabilities.

MFH: 2019Q3
Security: c97a940b-c392-11e9-bb38-000d3ab229d6
Sponsored by: Miles AS