debian/lxc-android-config.postinst: remove the old divert-removal code
We decided to use diversions, instead of override files, for udev rules in b4870a28 ("debian & etc: Divert udev overrides instead of relying on runtime preference"), reason being that we want a directory to be empty before letting snap read-write into it.
But as it turns out, long time ago Canonical used to use diversion, but
changed their mind in [1]. That means they put the divert-removal in the
postinst script. Coincidentally, the file name they used is exactly the
same as the one we used, which means our diversion is now no-op.
So, remove this diversion-removal code. Since we didn't put the conditional in the preinst code, this alone should be enough.