lib/utils/config/index.js/deleteValue
function deleteValue(key) {
  let config = getGlobalConfig();
  if (key && typeof key === 'string') {
    config = _.omit(config, [key]);
  } else if (key && _.isArray(key)) {
    config = _.omit(config, key);
  }
  // write to .serverlessrc file
  writeFileAtomic.sync(serverlessrcPath, JSON.stringify(config, null, 2));
  return config;
}