go/ssa: pass GOEXPERIMENT=aliastypeparams only on Go 1.23

On Go 1.24+ the GOEXPERIMENT is enabled by default, and will be
removed at tip.

Change-Id: Icb499612f459dfb3a6977a747878ca7bd2102f16
Reviewed-on: https://go-review.googlesource.com/c/tools/+/692476
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>

Author: cherrymui

go/ssa/builder_test.go

@@ -1115,8 +1115,10 @@ func TestGenericAliases(t *testing.T) {
 	cmd.Env = append(os.Environ(),
 		"GENERICALIASTEST_CHILD=1",
 		"GODEBUG=gotypesalias=1",
-		"GOEXPERIMENT=aliastypeparams",
 	)
+	if testenv.Go1Point() == 23 {
+		cmd.Env = append(cmd.Env, "GOEXPERIMENT=aliastypeparams")
+	}
 	out, err := cmd.CombinedOutput()
 	if len(out) > 0 {
 		t.Logf("out=<<%s>>", out)