Increase test coverage for nodejs-scan

We need to increase the test coverage for nodejs-scan to at least 60.0%.

remote: Total 61 (delta 41), reused 45 (delta 25), pack-reused 0
➜  nodejs-scan git:(master) ✗ go test -cover
COVER| 13.3% [#_________]
PASS | gitlab.com/gitlab-org/security-products/analyzers/nodejs-scan/v2 0.275s