DOC: update whatsnew style, minore codestyle change

Author: Scorpil

doc/source/whatsnew/v0.22.0.txt

@@ -23,7 +23,7 @@ New features
 ``get_dummies`` now supports ``dtype`` argument
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-The :func:`get_dummies` now accepts a ``dtype`` argument, which specifies a specific dtype for the new columns. When ``dtype`` is not specified or ``None``, the dtype will be ``uint8`` as before. (:issue:`18330`)
+The :func:`get_dummies` now accepts a ``dtype`` argument, which specifies a dtype for the new columns. The default remains uint8. (:issue:`18330`)
 
 .. ipython:: python
 

pandas/core/reshape/reshape.py

@@ -864,8 +864,7 @@ def _get_dummies_1d(data, prefix, prefix_sep='_', dummy_na=False,
 
     if dtype is None:
         dtype = np.uint8
-    else:
-        dtype = np.dtype(dtype)
+    dtype = np.dtype(dtype)
 
     if is_object_dtype(dtype):
         raise ValueError("dtype=object is not a valid dtype for get_dummies")