Specify python3 version in apt install commands

The default python3 is python 3.10 in debian:testing but this python version
has issues with installing meson and is ahead of gLinux. Specify 3.9 to
keep the version in CI the same as developers workstation.

Change-Id: Ibe2575c214499147134f82276964a34ae9856e6c
1 file changed