DOC: ignore deprecation warnings for convert_objects (GH10265)

Author: jorisvandenbossche

doc/source/whatsnew/v0.11.0.txt

@@ -103,6 +103,7 @@ Conversion
 Mixed Conversion
 
 .. ipython:: python
+   :okwarning:
 
    df3['D'] = '1.'
    df3['E'] = '1'
@@ -116,6 +117,7 @@ Mixed Conversion
 Forcing Date coercion (and setting ``NaT`` when not datelike)
 
 .. ipython:: python
+   :okwarning:
 
    from datetime import datetime
    s = Series([datetime(2001,1,1,0,0), 'foo', 1.0, 1,
@@ -328,4 +330,3 @@ Enhancements
 See the :ref:`full release notes
 <release>` or issue tracker
 on GitHub for a complete list.
-