www/node8: Update 8.14.0_1 -> 8.15.0

The 8.14.0 security release introduced some unexpected breakages on the
8.x release line. This is a special release to fix a regression in the
HTTP binary upgrade response body and add a missing CLI flag to adjust
the max header size of the http parser.

https://nodejs.org/en/blog/release/v8.15.0/

Sponsored by: Miles AS