CLN: Cleanup toplevel namespace shims (pandas-dev#23386)

Removes the following:

* pandas.types
* pandas.computation
* pandas.util.decorators

xref pandas-devgh-16157.
xref pandas-devgh-16250.

Author: gfyoung

doc/source/whatsnew/v0.24.0.txt

@@ -944,6 +944,7 @@ Removal of prior version deprecations/changes
 - :meth:`Index.repeat` and :meth:`MultiIndex.repeat` have renamed the ``n`` argument to ``repeats`` (:issue:`14645`)
 - The ``Series`` constructor and ``.astype`` method will now raise a ``ValueError`` if timestamp dtypes are passed in without a frequency (e.g. ``np.datetime64``) for the ``dtype`` parameter (:issue:`15987`)
 - Removal of the previously deprecated ``as_indexer`` keyword completely from ``str.match()`` (:issue:`22356`, :issue:`6581`)
+- The modules ``pandas.types``, ``pandas.computation``, and ``pandas.util.decorators`` have been removed (:issue:`16157`, :issue:`16250`)
 - Removed the ``pandas.formats.style`` shim for :class:`pandas.io.formats.style.Styler` (:issue:`16059`)
 - :func:`pandas.pnow`, :func:`pandas.match`, :func:`pandas.groupby`, :func:`pd.get_store`, ``pd.Expr``, and ``pd.Term`` have been removed (:issue:`15538`, :issue:`15940`)
 - :meth:`Categorical.searchsorted` and :meth:`Series.searchsorted` have renamed the ``v`` argument to ``value`` (:issue:`14645`)

pandas/computation/__init__.py

@@ -135,20 +135,6 @@ def test_TimeGrouper(self):
             pd.TimeGrouper(freq='D')
 
 
-class TestTypes(object):
-
-    def test_deprecation_access_func(self):
-        with tm.assert_produces_warning(
-                FutureWarning, check_stacklevel=False):
-            from pandas.types.concat import union_categoricals
-            c1 = pd.Categorical(list('aabc'))
-            c2 = pd.Categorical(list('abcd'))
-            union_categoricals(
-                [c1, c2],
-                sort_categories=True,
-                ignore_order=True)
-
-
 class TestCDateRange(object):
 
     def test_deprecation_cdaterange(self):