[CI] install python3-pil from apt in servergitmirrors
[CI] install python3-pil from apt in servergitmirrors

New version would need to be compiled, otherwise.

fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver