mm: fix clean_record_shared_mapping_range kernel-doc

Turn the a), b) into an unordered ReST list and remove the unnecessary
'Note:' prefix.

Link: https://lkml.kernel.org/r/20230818200630.2719595-4-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>