dashboard: vulndb runs only on 1.18 (or greater)

Since the x/vulndb repo is for the Go team only, we
do not need to support older Go versions. So run only
on Go 1.18.

Change-Id: I6c62ab70a0354afe8bfc8150206947f05ebbffc4
Reviewed-on: https://go-review.googlesource.com/c/build/+/393638
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

dashboard/builders.go

@@ -1585,7 +1585,7 @@ func init() {
 		HostType: "host-linux-bullseye",
 		tryBot:   defaultTrySet(),
 		buildsRepo: func(repo, branch, goBranch string) bool {
-			if repo == "vulndb" && atMostGo1(goBranch, 16) {
+			if repo == "vulndb" && atMostGo1(goBranch, 17) {
 				// The vulndb repo is for use only by the Go team,
 				// so it doesn't need to work on older Go versions.
 				return false

dashboard/builders_test.go

@@ -614,10 +614,10 @@ func TestBuilderConfig(t *testing.T) {
 		{b("linux-amd64-nocgo", "build"), none},
 		{b("linux-386-longtest", "build"), none},
 
-		// x/vulndb isn't tested on Go 1.16 and older.
-		{b("linux-amd64@go1.16", "vulndb"), none},
-		{b("linux-amd64@go1.17", "vulndb"), both},
-		{b("linux-amd64-longtest@go1.16", "vulndb"), none},
+		// x/vulndb isn't tested on Go 1.17 and older.
+		{b("linux-amd64@go1.17", "vulndb"), none},
+		{b("linux-amd64@go1.18", "vulndb"), both},
+		{b("linux-amd64-longtest@go1.17", "vulndb"), none},
 		{b("linux-amd64-longtest", "vulndb"), onlyPost},
 
 		{b("js-wasm", "build"), none},