Update simann_example.swift

Corrected definition where shuffle() was invoking self.shuffle() instead of self.tour.shuffle(), which would left the example in a infinite loop of shuffle() invocation

Simulated annealing/simann_example.swift

@@ -138,7 +138,7 @@ extension Tour {
   }
 
   func shuffle() {
-    self.shuffle()
+    self.tour.shuffle()
   }
 }