Switch Win10 AlphaR2 bots to new Windows image.

This affects RadeonR9M470X.

Change-Id: I6d11ee553aced18494a07c5b8703060d105567f7
Reviewed-on: https://skia-review.googlesource.com/109809
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
2 files changed