Move spotless configuration out of build.gradle.kts

Spotless is not compatible with the Gradle configuration cache, so it should only be applied using an init script and not be included in the project's build config.

Also, the current spotless configuration [excludes an entire package][1] for seemingly no reason.

[1]: https://github.com/android/socialite/blob/85d11e853322b7afc0ca77ff2ac219389289d64f/build.gradle.kts#L35

Start by reading build.gradle.kts, focusing on the Spotless configuration and its package exclusion. Inspect the project’s build setup for the appropriate init-script entry point, then verify configuration-cache behavior and formatting coverage. Done means Spotless is no longer applied from the project build configuration and the unexplained exclusion is addressed.

Written by the indexing model from the issue text.