[DOCS] Evaluate ppa documentation

[eldonquijote]

• Ask on Slack and in the tech call if documentation about Updating deb package is still needed: https://islandora.github.io/documentation/technical-documentation/ppa-documentation/
• If it's not needed anymore, retire page

[rosiel]

I contacted Jonathan Green and confirmed the PPA is still functional in case we have to use it in the future. I propose that we add to the end of the "Background" section,

If you are running Ubuntu 20.04 or higher, installing a specially-compiled imagemagick is no longer necessary. We are leaving this page available in case in the future we have a need to package our own deb and add it to the Lyrasis PPA.

That sound ok?