remove reference to deprecated .ix from 10min.rst (pandas-dev#19452)

Author: timhoffm

doc/source/10min.rst

@@ -154,7 +154,7 @@ Selection
    While standard Python / Numpy expressions for selecting and setting are
    intuitive and come in handy for interactive work, for production code, we
    recommend the optimized pandas data access methods, ``.at``, ``.iat``,
-   ``.loc``, ``.iloc`` and ``.ix``.
+   ``.loc`` and ``.iloc``.
 
 See the indexing documentation :ref:`Indexing and Selecting Data <indexing>` and :ref:`MultiIndex / Advanced Indexing <advanced>`.