Example: rynz/node-test-protocol#6

In this example exists an empty .npmrc and when it is populated with registry= an error occurs:

npm ERR! 401 Unauthorized - GET https://npm.pkg.github.com/rynz/prettier - could not retrieve user by token

For whatever reason, the registry= is not being removed correctly like https://github.com/actions/setup-node/blob/master/src/authutil.ts#L41 is supposed to do.