docs/admin-guide/mm: remove useless markup
It is enough to use a file name to cross-reference another rst document.
Jon says:
The right things will happen in the HTML output, readers of the
plain-text will know immediately where to go, and we don't have to add
the label clutter.
Drop reference markup and unnecessary labels and use plain file names.
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Link: https://lore.kernel.org/r/20230201094156.991542-4-rppt@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>