pam: drop pam_loginuid from launch environment session

From https://bugzilla.redhat.com/show_bug.cgi?id=882385:

"The loginuid is for actual logins by people. Its not intended for
system use. All daemons should have loginuid set to -1, meaning that its
a system process and not related to activity by a person."

https://bugzilla.gnome.org/show_bug.cgi?id=693152