net: block three, retired, Symantec intermediates.

See https://bugzilla.mozilla.org/show_bug.cgi?id=966060

BUG=none

Review URL: https://codereview.chromium.org/152973003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248578 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248578