CLN: fix typo in asv benchmark of non_unique_sorted, which was not sorted

Author: qwhelan

Diff for: asv_bench/benchmarks/index_object.py

@@ -138,7 +138,7 @@ def setup(self, dtype):
         self.sorted = self.idx.sort_values()
         half = N // 2
         self.non_unique = self.idx[:half].append(self.idx[:half])
-        self.non_unique_sorted = self.sorted[:half].append(self.sorted[:half])
+        self.non_unique_sorted = self.sorted[:half].append(self.sorted[:half]).sort_values()
         self.key = self.sorted[N // 4]
 
     def time_boolean_array(self, dtype):