dashboard: limit windows-{386,amd64}-2012 to build at most Go 1.20

CL 468937 added a newer Windows 32-bit TryBot that will provide coverage
for the windows/386 port for Go 1.21 and newer. Stop the older Windows 8
builders from running on the relevant branches.

Updates golang/go#58007.
Fixes golang/go#58008.

Change-Id: I8664a74543b2225986586440ab027cda85b67a3e
Reviewed-on: https://go-review.googlesource.com/c/build/+/463579
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

dashboard/builders.go

@@ -2244,8 +2244,9 @@ func init() {
 			// of Go, hence the atLeastGo1 call below; versions of Go
 			// prior to 1.20 will use the *-oldcc variant instead. See
 			// issue 35006 for more details.
+			// Go 1.20 is also the last version with Windows 8/8.1 support. See proposal 57004.
 			return onlyGo(repo, branch, goBranch) &&
-				atLeastGo1(goBranch, 20)
+				atLeastGo1(goBranch, 20) && atMostGo1(goBranch, 20)
 		},
 		env: []string{"GOARCH=386", "GOHOSTARCH=386"},
 		tryBot: func(repo, branch, goBranch string) bool {
@@ -2348,8 +2349,9 @@ func init() {
 			// of Go, hence the atLeastGo1 call below; versions of Go
 			// prior to 1.20 will use the *-oldcc variant instead. See
 			// issue 35006 for more details.
+			// Go 1.20 is also the last version with Windows 8/8.1 support. See proposal 57004.
 			return onlyGo(repo, branch, goBranch) &&
-				atLeastGo1(goBranch, 20)
+				atLeastGo1(goBranch, 20) && atMostGo1(goBranch, 20)
 		},
 		env: []string{
 			"GOARCH=amd64",

dashboard/builders_test.go

@@ -101,7 +101,6 @@ func TestTrybots(t *testing.T) {
 				"linux-amd64-race",
 				"linux-arm64",
 				"openbsd-amd64-72",
-				"windows-386-2012",
 				"windows-386-2016",
 				"windows-amd64-2016",
 
@@ -152,7 +151,6 @@ func TestTrybots(t *testing.T) {
 				"linux-amd64-race",
 				"linux-arm64",
 				"openbsd-amd64-72",
-				"windows-386-2012",
 				"windows-386-2016",
 				"windows-amd64-2016",