ci: only install Python once in Windows setup script
ci: only install Python once in Windows setup script

Previously, the script would install the python package without a
version specifier, then attempt to install a specific version (3.9.0),
but this would fail because the first step installed a newer Python
version:

  A newer version of python (v3.10.4) is already installed.

  Use --allow-downgrade or --force to attempt to install older versions,
  or use side by side to allow multiple versions.

  Chocolatey installed 0/1 packages. 1 packages failed.

Remove the first unversioned step so we always get the requested version
of Python only.

BUG=None
TEST=kokoro CI

Change-Id: I95b224926ee9ebcaacdb7d6c2716381a46ec467c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3657850
Reviewed-by: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm