Document uninstallation from source

Siril version: f320f141

Operating System: Ubuntu 22.04

Package: [see below]

Description of the bug

I installed Siril 1.0.3 by building from source on ubuntu. I ran into astrometry issues and was happy to see 1.0.5 now available. I installed Siril 1.0.5 from Ubuntu repo. When I start Siril from the applications list, it's still 1.0.3. I can't find instructions for removing Siril 1.0.3. I tried make remove and make uninstall both before and after checking out master.

Can you please update the readme with uninstallation instructions or post them on this issue?