CVE-2018-8768,Ipython: Mark as no-dsa for Wheezy.

Ipython in Wheezy lacks sanitization of untrusted HTML completely which means
in theory this CVE does not apply. However due to the absence of sanitization
it is recommended not to use Ipython's notebook with untrusted content. This
issue is no-dsa because it cannot be determined if Wheezy is still affected, a
fix appears to be to intrusive though. We recommend to upgrade to a newer
version instead.