DOC: small doc fixed (pandas-dev#13886)

Author: sinhrks

doc/source/whatsnew/v0.19.0.txt

@@ -301,7 +301,7 @@ For ``MultiIndex``, values are dropped if any level is missing by default. Speci
 
 ``Index.astype()`` now accepts an optional boolean argument ``copy``, which allows optional copying if the requirements on dtype are satisfied (:issue:`13209`)
 
-.. _whatsnew_0170.gbq:
+.. _whatsnew_0190.gbq:
 
 Google BigQuery Enhancements
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -342,7 +342,7 @@ Other enhancements
 - Consistent with the Python API, ``pd.read_csv()`` will now interpret ``+inf`` as positive infinity (:issue:`13274`)
 - The ``DataFrame`` constructor will now respect key ordering if a list of ``OrderedDict`` objects are passed in (:issue:`13304`)
 - ``pd.read_html()`` has gained support for the ``decimal`` option (:issue:`12907`)
-- A function :func:`union_categorical` has been added for combining categoricals, see :ref:`Unioning Categoricals<categorical.union>` (:issue:`13361`, :issue:`:13763`, issue:`13846')
+- A function :func:`union_categorical` has been added for combining categoricals, see :ref:`Unioning Categoricals<categorical.union>` (:issue:`13361`, :issue:`:13763`, issue:`13846`)
 - ``Series`` has gained the properties ``.is_monotonic``, ``.is_monotonic_increasing``, ``.is_monotonic_decreasing``, similar to ``Index`` (:issue:`13336`)
 - ``DataFrame.to_sql()`` now allows a single value as the SQL type for all columns (:issue:`11886`).
 - ``Series.append`` now supports the ``ignore_index`` option (:issue:`13677`)