dashboard: switch host-freebsd-13_0-big to e2-standard-4 machines

This reduces the freebsd-amd64-race builder to 4 vCPUs instead of 16,
which should also reduce the default GOMAXPROCS and default
-test.parallel settings on that builder.

The theory is that by switching to a standard CPU-to-RAM ratio, we
will avoid OOMing in memory-bound x/tools tests, which scale their
parallelism by GOMAXPROCS rather than the machine's total RAM size.

For golang/go#49347

Change-Id: I6960efc5636fef7d2e6197aee33212a7823f0970
Reviewed-on: https://go-review.googlesource.com/c/build/+/382058
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

dashboard/builders.go

@@ -322,8 +322,8 @@ var Hosts = map[string]*HostConfig{
 	},
 	"host-freebsd-13_0-big": &HostConfig{
 		VMImage:            "freebsd-amd64-130-stable-20211230",
-		Notes:              "Same as host-freebsd-13_0, but on e2-highcpu-16",
-		machineType:        "e2-highcpu-16", // 16 vCPUs, 16 GB mem
+		Notes:              "Same as host-freebsd-13_0, but on e2-standard-4",
+		machineType:        "e2-standard-4", // 4 vCPUs, 16 GB mem
 		buildletURLTmpl:    "https://storage.googleapis.com/$BUCKET/buildlet.freebsd-amd64",
 		goBootstrapURLTmpl: "https://storage.googleapis.com/$BUCKET/go1.4-freebsd-amd64.tar.gz",
 		SSHUsername:        "gopher",