VS: Select latest Windows SDK even when targeting Windows 8.1 and below

The policy added by commit f90c8ab54e (VS: Select latest available
Windows SDK version by default, 2023-04-03, v3.27.0-rc1~206^2~1) applied
only when targeting Windows 10+.  Apply it to older versions too.

Fixes: #25170
Issue: #16202
4 files changed