[CfT] Fix CfT specific policy path on Windows

https://crrev.com/c/5008236 introduced Chrome for Testing specific policy path that is different from both Chrome and Chromium policy paths, however, that change only affects Linux build while the Windows CfT build still uses Chromium policy path in registry.

This CL changes policy path CfT uses on Windows to
SOFTWARE\Policies\Google\Chrome for Testing

Bug: 326275044
Change-Id: I0eea603b88781e0f96dbab024c83a3fa2236ed5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5315959
Commit-Queue: Peter Kvitek <kvitekp@chromium.org>
Reviewed-by: Yann Dago <ydago@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1264621}