tools/memory-model: simple.txt: Fix stale reference to recipes-pairs.txt

There has never been recipes-paris.txt at least since v5.11.
Fix the typo.
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/memory-model/Documentation/simple.txt

@@ -266,5 +266,5 @@ More complex use cases
 ======================
 
 If the alternatives above do not do what you need, please look at the
-recipes-pairs.txt file to peel off the next layer of the memory-ordering
+recipes.txt file to peel off the next layer of the memory-ordering
 onion.