Use new Canary flag in canary task driver

Bug: skia:12630
Change-Id: Ie4d4d9a62b4152b8ce3ebb5edebfe9aab88a2a25
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/469858
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>

infra/bots/task_drivers/canary/canary.go

@@ -94,6 +94,7 @@ func main() {
 			DryRun:            true,
 			NoEmail:           true,
 			NoResolveRevision: true,
+			Canary:            true,
 		}
 		if err := td.Do(ctx, td.Props(fmt.Sprintf("Trigger canary roll%s", retryText)).Infra(), func(ctx context.Context) error {
 			return manualRollDB.Put(&req)