basics.rst: describe include object -> str

Author: jorisvandenbossche

doc/source/user_guide/basics.rst

@@ -590,7 +590,7 @@ arguments. The special value ``all`` can also be used:
 
 .. ipython:: python
 
-    frame.describe(include=["object"])
+    frame.describe(include=["str"])
     frame.describe(include=["number"])
     frame.describe(include="all")