Don't format generated code

[krzema12]

Reformatting with ktlint together with some Gradle settings (see the below commit) caused this: #382. For now I reverted the Gradle settings, at the cost of worse performance. We could instead disable formatting of generated code and bring back what was reverted here: https://github.com/krzema12/github-actions-kotlin-dsl/commit/3c3d38a88a0794d9d846015245bdf723cae1ad17