remove ppa install for GHA and fix U22 log files

[maloel]

GHA is failing recently in the Prebuild step for U20 builds:

> Run sudo add-apt-repository --yes ppa:ubuntu-toolchain-r/test;
Cannot add PPA: 'ppa:~ubuntu-toolchain-r/ubuntu/test'.
The team named '~ubuntu-toolchain-r' has no PPA named 'ubuntu/test'
Please choose from the following available PPAs:
...

In the build, we have sudo add-apt-repository --yes ppa:ubuntu-toolchain-r/test;

It is in our installation.md, but it’s under “On Ubuntu 14.04” section… and another installation guide for Ubuntu makes no mention of it.

Tracked on [LRS-929]

[Nir-Az]

LGTM