Revert "Modify fix_encodng to make it use fix_win_sys_argv for python2 only and"

This reverts commit 20815505e6.

Reason for revert:
This is not necessary after https://crrev.com/c/1929653

Original change's description:
> Modify fix_encodng to make it use fix_win_sys_argv for python2 only and
> not for python3 on windows.
>
> The function works around <https://bugs.python.org/issue2128>, and the bug is fixed for python3 now.
>
> Bug: 1182016
> Change-Id: I3880843b109d5b9779e5bbd1e39a3132f925ecc4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2738234
> Commit-Queue: Momo Sasaki <momosasaki@google.com>
> Reviewed-by: Dirk Pranke <dpranke@google.com>
> Reviewed-by: Junji Watanabe <jwata@google.com>
> Reviewed-by: Takuto Ikuta <tikuta@chromium.org>

Bug: 1182016
Change-Id: I153640b174a78990e39b3597208b6785003ca321
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2738936
Reviewed-by: Junji Watanabe <jwata@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>

fix_encoding.py

@@ -380,7 +380,6 @@ def fix_encoding():
 
   if sys.platform == 'win32':
     encoding = sys.getdefaultencoding()
-    if sys.version_info[0] == 2:
-      ret &= fix_win_sys_argv(encoding)
+    ret &= fix_win_sys_argv(encoding)
     ret &= fix_win_console(encoding)
   return ret