refactor: replace indexOfs

lib/config/migration.js

lib/config/presets.js

lib/config/validation.js

lib/logger/config-serializer.js

lib/logger/pretty-stdout.js

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

lib/platform/github/index.js

lib/workers/branch/schedule.js

lib/workers/pr/index.js

lib/workers/repository/finalise/prune.js

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