src: drop CNNIC+StartCom certificate whitelisting

Remove the CNNIC certificates again and remove the whitelist from commit
3beb880 ("crypto: add cert check to CNNIC Whitelist") from June 2015.

Backport-PR-URL: #19633
PR-URL: #19322
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: bnoordhuis