build: unbreak --with-intl=system-icu build

Include directories are configured by the tools/icu/icu-*.gyp files.
The v8.gyp file doesn't need to add them and in fact the way it did
that breaks when building against an external copy of ICU.

Fixes: https://github.com/nodejs/node/issues/28052
PR-URL: https://github.com/nodejs/node/pull/28118


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>