Debian's and Ubuntu's gdms differ about updating .dmrc

[geofft]

Debian's gdm3 2.30.5-10 seems to update ~/.dmrc with the session you just chose (even if you didn't explicitly pick one, and it defaulted to /var/cache/gdm/$USER/dmrc).

Ubuntu's gdm 2.32.1-0ubuntu3.2 seems not to.

I think Debian's behavior is more correct here, so we should see if that's a Debian patch not in Ubuntu, a regression in upstream 2.32 from upstream 2.30, or what. (Neither's behavior is actually correct)