ext4: remove the repeated comment of ext4_trim_all_free

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Wang Jianchao <wangjianchao@kuaishou.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210724074124.25731-4-jianchao.wan9@gmail.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>