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>
diff --git a/infra/bots/gen_tasks.go b/infra/bots/gen_tasks.go
index 70195ad..7d85a99 100644
--- a/infra/bots/gen_tasks.go
+++ b/infra/bots/gen_tasks.go
@@ -213,6 +213,7 @@
 		if os == "Win10" {
 			// Transition to new Win image by model name.
 			_, ok = map[string]bool{
+				"AlphaR2":       true,
 				"NUC5i7RYH":     true,
 				"NUC6i5SYK":     true,
 				"NUCD34010WYKH": true,