build: remove cares headers from tarball

The bundled c-ares isn't very suitable for consumption by addons,
isn't kept stable, and isn't exported on windows.

PR-URL: https://github.com/nodejs/node/pull/10283
Refs: https://github.com/nodejs/node-gyp/pull/1055


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>