This feature was originally introduced by
f961ffd9 as a fix for FS#12898
<https://bugs.archlinux.org/task/12898

>.

As of today, it is broken because of the `q.SessionID IS NULL` condition
in the WHERE clause, which can’t be true because SessionID is not
nullable. As a consequence, the session limit was not applied.

The fact the absence of the session limit hasn’t caused any issue so
far, and hadn’t even been noticed, suggests the feature is unneeded.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>