UIF, update-manager changes to show apt news message and adapt slightly the layout

[Sebastien Bacher]

Dear documentation and translations team,

We are requesting an UIF to fix 
https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1990450

Screenshot before and after
https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1990450/+attachment/5704318/+files/before.png
https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1990450/+attachment/5704319/+files/after.png

Basically a section is displayed now at the top to show apt news message 
and the tabs are the bottom got replaced by different section in the 
same entry (needed to accomodate the extra news section)

Cheers,
Sebastien Bacher