fix: Revert "feat: additionalBranchPrefix"

docs/usage/configuration-options.md

docs/usage/configuration-templates.md

lib/config/__snapshots__/migration.spec.ts.snap

lib/config/definitions.ts

lib/config/migration.spec.ts

lib/config/migration.ts

lib/config/validation.ts

lib/datasource/docker/index.ts

lib/manager/buildkite/index.ts

lib/manager/cargo/index.ts

lib/manager/homebrew/index.ts

lib/util/template/index.ts

lib/workers/repository/updates/flatten.ts