i3-dmenu-desktop test: Do not autostart i3
This actually fixes a hang that happens on my machine for some reason.
Regardless, starting i3 is not necessary for this test.
# and sends the command to i3 for execution.
# Ticket: #5152, #5156
# Bug still in: 4.21-17-g389d555d
-use i3test;
+use i3test i3_autostart => 0;
use i3test::Util qw(slurp);
use File::Temp qw(tempfile tempdir);
use POSIX qw(mkfifo);
