Use the API URL from the environment if it is present.

lib/config-utils.test.js

@@ -40,6 +40,7 @@ const sampleApiDetails = {
     auth: "token",
     externalRepoAuth: "token",
     url: "https://github.example.com",
+    apiURL: undefined,
 };
 const gitHubVersion = { type: util.GitHubVariant.DOTCOM };
 // Returns the filepath of the newly-created file