DOC: Update excel read dependency on xlrd

Since 98f65b1,
``xlrd`` handles reading both ``.xls`` and ``.xlsx`` Excel Files.

Author: davidshinn

doc/source/io.rst

@@ -1494,7 +1494,8 @@ any pickled pandas object (or any other pickled object) from file:
 Excel files
 -----------
 
-The ``read_excel`` method can read an Excel 2003 file using the ``xlrd`` Python
+The ``read_excel`` method can read Excel 2003 (``.xls``) and
+Excel 2007 (``.xlsx``) files using the ``xlrd`` Python
 module and use the same parsing code as the above to convert tabular data into
 a DataFrame. See the :ref:`cookbook<cookbook.excel>` for some
 advanced strategies
@@ -1516,9 +1517,6 @@ advanced strategies
 
         read_excel('path_to_file.xls', 'Sheet1', index_col=None, na_values=['NA'])
 
-To read sheets from an Excel 2007 file, you can pass a filename with a ``.xlsx``
-extension, in which case the ``openpyxl`` module will be used to read the file.
-
 It is often the case that users will insert columns to do temporary computations
 in Excel and you may not want to read in those columns. `read_excel` takes
 a `parse_cols` keyword to allow you to specify a subset of columns to parse.