Documentation: ext4: atomic_writes: Demote last three sections

Documentation: ext4: atomic_writes: Demote last three sections

Last three sections of atomic block writes documentation are adorned as
first-level title headings, which erroneously increase toctree entries
in overview.rst. Demote them.

Fixes: 0bf1f51e34c4 ("ext4: Add atomic block write documentation")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250620105643.25141-5-bagasdotme@gmail.com