We want to have the system-level npmrc located at /etc/npmrc.
By default, npm looks for it in /usr/etc/npmrc,
so we placed a symlink to /etc/npmrc there.
However, we are the only known package that has anything in /usr/etc,
which confuses and/or breaks various tooling (see related bug).
This gets rid of the symlink,
and instead uses "builtin"-level configuration of npm
to cause it to load the system-level configuration from /etc/npmrc.
Related: rhbz#2177776
