Documentation/vm/page_migration: update reference to numa_maps + fix download URI

With man-pages-3.07, the numa_maps documentation home is now proc(5), so
the reference in Documentation/vm/page_migration needs updating.
(Cliff/Lee are removing numa_maps.5 from the numactl package.) Also, the
download location for the numactl package changed a while back.  This
patch fixes both things, as well as a typo (provided-->provides).

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Cliff Wickman <cpw@sgi.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>