all: remove skipIfShort

We don't have any tests using it.

Change-Id: I72b24d505c0d9ec5cf9fce883bc04ed10f6bfd4f
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/595455
Auto-Submit: Zvonimir Pavlinovic <zpavlinovic@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Maceo Thompson <maceothompson@google.com>

all_test.go

@@ -92,9 +92,3 @@ func rungo(t *testing.T, args ...string) {
 		t.Fatalf("%v: %v\n%s", cmd, err, output)
 	}
 }
-
-func skipIfShort(t *testing.T) {
-	if testing.Short() {
-		t.Skipf("skipping: short mode")
-	}
-}