BUG: Fixup bench for deprecation (#27207)

Author: TomAugspurger

asv_bench/benchmarks/categoricals.py

@@ -1,5 +1,3 @@
-import warnings
-
 import numpy as np
 import pandas as pd
 import pandas.util.testing as tm
@@ -133,15 +131,10 @@ def setup(self):
 
         self.s_str = pd.Series(tm.makeCategoricalIndex(N, ncats)).astype(str)
         self.s_str_cat = self.s_str.astype('category')
-        with warnings.catch_warnings(record=True):
-            self.s_str_cat_ordered = self.s_str.astype('category',
-                                                       ordered=True)
-
+        self.s_str_cat_ordered = self.s_str_cat.cat.as_ordered()
         self.s_int = pd.Series(np.random.randint(0, ncats, size=N))
         self.s_int_cat = self.s_int.astype('category')
-        with warnings.catch_warnings(record=True):
-            self.s_int_cat_ordered = self.s_int.astype('category',
-                                                       ordered=True)
+        self.s_int_cat_ordered = self.s_int_cat.cat.as_ordered()
 
     def time_rank_string(self):
         self.s_str.rank()