The description of 'commit' mount option dates back to ext3 times.
Update the description to match current meaning for ext4.

Reported-by: Paul Richards <paul.richards@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191218111210.14161-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Introduces the case-insensitive features on ext4 for system
administrators.  Explain the minimum of design decisions that are
important for sysadmins wanting to enable this feature.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Move the ext4 mount option and other administrative stuff to the Linux
administrator's guide.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>