refactor: array concatenation (#1601)

lib/config/index.js

lib/config/migrate-validate.js

lib/config/presets.js

lib/config/validation.js

lib/manager/index.js

lib/manager/travis/package.js

lib/platform/github/gh-got-wrapper.js

lib/platform/gitlab/gl-got-wrapper.js

lib/workers/branch/commit.js

lib/workers/dep-type/index.js

lib/workers/package-file/index.js

lib/workers/repository/index.js

lib/workers/repository/init/base.js

lib/workers/repository/onboarding/pr/config-description.js

lib/workers/repository/updates/branchify.js

lib/workers/repository/updates/determine.js