f2fs: remove batched_trim_sections node description

It's deprecated since commit 377224c4 ("f2fs: don't split checkpoint in fstrim").
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -190,12 +190,6 @@ Description:	Controls the memory footprint used by free nids and cached
 		nat entries. By default, 1 is set, which indicates
 		10 MB / 1 GB RAM.
 
-What:		/sys/fs/f2fs/<disk>/batched_trim_sections
-Date:		February 2015
-Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
-Description:	Controls the trimming rate in batch mode.
-		<deprecated>
-
 What:		/sys/fs/f2fs/<disk>/cp_interval
 Date:		October 2015
 Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>