build: fix pkg-config search for libnghttp2

The configure script was searching for 'nghttp2' whereas the actual name
of the package is 'libnghttp2'.

This change also removes the hack for libcares in one fell swoop.

Co-Authored-By: legendecas <legendecas@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/30145
Fixes: https://github.com/nodejs/node/issues/30113


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>