test: delete unused test helper file

test/helpers/mock-github.js

@@ -1,16 +0,0 @@
-import nock from 'nock';
-
-/**
- * Retun a `nock` object setup to respond to a github authentication request. Other expectation and responses can be chained.
- *
- * @param {String} [githubToken='GH_TOKEN'] The github token to return in the authentication response.
- * @param {String} [githubUrl='https://api.github.com'] The url on which to intercept http requests.
- * @return {Object} A `nock` object ready to respond to a github authentication request.
- */
-export default function authenticate({
-  githubToken = 'GH_TOKEN',
-  githubUrl = 'https://api.github.com',
-  githubApiPathPrefix = '',
-} = {}) {
-  return nock(`${githubUrl}/${githubApiPathPrefix}`, {reqheaders: {Authorization: `token ${githubToken}`}});
-}