[W520] should disable [W513]

[mcm1957]

[W513] "gulpfile.js" found in repo! Think about migrating to @iobroker/adapter-dev package
[W520] "gulpfile.js" found in repo but "gulp" not found at devDependencies at package.json. Check whether it can be removed.

If gulp is not listed as dependency it is most likely not used. So a migration should not be recommended.