windows: drop some py2 registry module importing

The comment was actually backwards- `winreg` is importable on py3, and is
already imported by mercurial/windows.py.

mercurial/scmwindows.py

@@ -1,4 +1,5 b''
 import os
+import winreg  # pytype: disable=import-error
 
 from typing import (
     List,
@@ -15,14 +16,6 b' from . import ('
 if pycompat.TYPE_CHECKING:
     from . import ui as uimod
 
-try:
-    import _winreg as winreg  # pytype: disable=import-error
-
-    winreg.CloseKey
-except ImportError:
-    # py2 only
-    import winreg  # pytype: disable=import-error
-
 # MS-DOS 'more' is the only pager available by default on Windows.
 fallbackpager = b'more'