cmd/govulncheck: clean up test

staticcheck was complaining

Change-Id: I67c965b01f67ea907fdb5fa9b7a37447a49b9bde
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/575135
Run-TryBot: Zvonimir Pavlinovic <zpavlinovic@google.com>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

cmd/govulncheck/test_utils.go

@@ -118,7 +118,7 @@ func loadConfig(path string) (*config, error) {
 	if err := json.Unmarshal(b, &cfg); err != nil {
 		return nil, err
 	}
-	for i, _ := range cfg.Fixups {
+	for i := range cfg.Fixups {
 		cfg.Fixups[i].init()
 	}
 	return &cfg, nil