Revert unnecessary changes from 22019 (#24802)

At the time, #22019 seemed to
break API in a few places. Since then, those API breaking changes have
disappeared, so the changes to the tests and the release note are no
longer necessary.

Closes #24789

Author: TomAugspurger

doc/source/whatsnew/v0.24.0.rst

@@ -1163,36 +1163,6 @@ data is incompatible with a passed ``dtype=`` (:issue:`15832`)
     ...
     OverflowError: Trying to coerce negative values to unsigned integers
 
-.. _whatsnew_0240.api.crosstab_dtypes:
-
-Crosstab Preserves Dtypes
-^^^^^^^^^^^^^^^^^^^^^^^^^
-
-:func:`crosstab` will preserve now dtypes in some cases that previously would
-cast from integer dtype to floating dtype (:issue:`22019`)
-
-*Previous Behavior*:
-
-.. code-block:: ipython
-
-    In [3]: df = pd.DataFrame({'a': [1, 2, 2, 2, 2], 'b': [3, 3, 4, 4, 4],
-       ...:                    'c': [1, 1, np.nan, 1, 1]})
-    In [4]: pd.crosstab(df.a, df.b, normalize='columns')
-    Out[4]:
-    b    3    4
-    a
-    1  0.5  0.0
-    2  0.5  1.0
-
-*New Behavior*:
-
-.. code-block:: ipython
-
-    In [3]: df = pd.DataFrame({'a': [1, 2, 2, 2, 2],
-       ...:                    'b': [3, 3, 4, 4, 4],
-       ...:                    'c': [1, 1, np.nan, 1, 1]})
-    In [4]: pd.crosstab(df.a, df.b, normalize='columns')
-
 .. _whatsnew_0240.api.concat_categorical:
 
 Concatenation Changes

pandas/tests/frame/test_axis_select_reindex.py

@@ -717,7 +717,7 @@ def test_align_int_fill_bug(self):
 
         result = df1 - df1.mean()
         expected = df2 - df2.mean()
-        assert_frame_equal(result.astype('f8'), expected)
+        assert_frame_equal(result, expected)
 
     def test_align_multiindex(self):
         # GH 10665

pandas/tests/reshape/test_pivot.py

@@ -1573,9 +1573,8 @@ def test_crosstab_normalize(self):
                               full_normal)
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize='index'),
                               row_normal)
-        tm.assert_frame_equal(
-            pd.crosstab(df.a, df.b, normalize='columns').astype('f8'),
-            col_normal)
+        tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize='columns'),
+                              col_normal)
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize=1),
                               pd.crosstab(df.a, df.b, normalize='columns'))
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize=0),
@@ -1608,7 +1607,7 @@ def test_crosstab_normalize(self):
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize='index',
                                           margins=True), row_normal_margins)
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize='columns',
-                                          margins=True).astype('f8'),
+                                          margins=True),
                               col_normal_margins)
         tm.assert_frame_equal(pd.crosstab(df.a, df.b, normalize=True,
                                           margins=True), all_normal_margins)