Subiquity snap doesn't stage language-selector-common nor locales
packages.
Attempting to run those commands require respecting the env previously
prepared by the caller, as well as fixing the commands paths
(or changing the PATH env var in the env preparation step).
Since the apt commands were already ran with a fixed path,
I'm applying the same principle in here.
Yet, for now, Jammy doesn't ship the l-s-c package seeded,
so a condition was preserved to avoid future crashes.
2e67005403