Only translate uniform block to StructuredBuffer when system is
Windows 10 and later.

Bug: angleproject:3682
Change-Id: I27e3f4503392791883a44e1d486ffe9512e04bd8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1984863
Commit-Queue: Xinghua Cao <xinghua.cao@intel.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>