Documentation: numaperf: eliminate duplicated word

Drop the duplicated word "not".
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: linux-mm@vger.kernel.org
Cc: Mike Rapoport <rppt@kernel.org>
Link: https://lore.kernel.org/r/20200707180414.10467-2-rdunlap@infradead.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/mm/numaperf.rst

@@ -129,7 +129,7 @@ will create the following directory::
 
 	/sys/devices/system/node/nodeX/memory_side_cache/
 
-If that directory is not present, the system either does not not provide
+If that directory is not present, the system either does not provide
 a memory-side cache, or that information is not accessible to the kernel.
 
 The attributes for each level of cache is provided under its cache