www/node: Update 9.3.0 -> 9.4.0

https://nodejs.org/en/blog/release/v9.4.0/

While here, pet portlint:

• move ONLY_FOR_ARCHS
• remove USES_LDCONFIG (node.js doesn't install a .so)

Approved by: mat (co-mentor)
Differential Revision: https://reviews.freebsd.org/D14050