Revert "Triage CVE-2020-1765, CVE-2020-1766 & CVE-2020-1767 in otrs2 in jessie LTS."

otrs2 in Jessie is not non-free, thus while the issue might be indeed
no-dsa and not warranting a DLA on it's own, the reason must/should be
another one.

This reverts commit cae6b097.