Remove legacy scipy compatt (#30072)

Author: jbrockmendel

pandas/core/nanops.py

@@ -1248,10 +1248,9 @@ def _pearson(a, b):
         return np.corrcoef(a, b)[0, 1]
 
     def _kendall(a, b):
+        # kendallttau returns a tuple of the tau statistic and pvalue
         rs = kendalltau(a, b)
-        if isinstance(rs, tuple):
-            return rs[0]
-        return rs
+        return rs[0]
 
     def _spearman(a, b):
         return spearmanr(a, b)[0]