crypto: remove root_cert_store from node_crypto.h

root_cert_store is defined as extern in node_crypto.h but only used in
node_crypto.cc. It is then set using SSL_CTX_set_cert_store. The only
usages of SSL_CTX_get_cert_store are in node_crypto.cc which would all
be accessing the same X509_STORE through the root_cert_store pointer as
far as I can tell. Am I missing something here?

This commit suggests removing it from the header and making it static
in node_crypto.cc.

PR-URL: https://github.com/nodejs/node/pull/13194


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