fix docs

Author: microslaw

doc/source/user_guide/indexing.rst

@@ -712,10 +712,9 @@ as a string.
 
 .. ipython:: python
 
-   1/0
     df2 = pd.DataFrame({'col1': [9, 8, 7, 6],
                         'weight_column': [0.5, 0.4, 0.1, 0]})
-    df2.sample(n=3, weights='weight_column')
+    df2.sample(n=2, weights='weight_column')
 
 ``sample`` also allows users to sample columns instead of rows using the ``axis`` argument.