fix indention in directive

Author: topper-123

doc/source/whatsnew/v0.25.0.rst

@@ -540,7 +540,7 @@ with :attr:`numpy.nan` in the case of an empty :class:`DataFrame` (:issue:`26397
 
 .. ipython:: python
 
-    df.describe()
+   df.describe()
 
 ``__str__`` methods now call ``__repr__`` rather than vice versa
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^