e2scrub: honor fstrim setting in e2scrub.conf

e2scrub: honor fstrim setting in e2scrub.conf

The systemd service unconditionally passes -t to e2scrub, forcing
fstrim to run after every scrub regardless of the fstrim setting
in /etc/e2scrub.conf. Removing the hardcoded flag will allow users to
control the behavior via the configuration file.

Signed-off-by: Samuel Smith <satlug@net153.net>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20250628051415.3015410-1-satlug@net153.net
Signed-off-by: Theodore Ts'o <tytso@mit.edu>