[infra] Update OS dimension for Windows GCE VMs

Change-Id: I8fc479bc86a144c8eaf19f5954b9c9da79d0ff22
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/985517
Commit-Queue: Eric Boren <borenet@google.com>
Commit-Queue: Daniel Dilan <danieldilan@google.com>
Reviewed-by: Daniel Dilan <danieldilan@google.com>
Auto-Submit: Eric Boren <borenet@google.com>
(cherry picked from commit 1bfa68946da062bf1d3bb80ad657723a74866f90)
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/985519