Revert "Two CVEs CVE-2019-5870 and CVE-2019-13720 are associated as well with...

Revert "Two CVEs CVE-2019-5870 and CVE-2019-13720 are associated as well with qtwebengine-opensource-src"

It is explicitly not supported security wise, and it does not make much
sense to only track those two CVEs while more CVEs would technically
affect qtwebengine-opensource-src further. So rather ignore it for
security issues tracking now.

This reverts commit 16987dc6.