Updated to Spotless 3.0.0.
Updated to Spotless 3.0.0.

- added removeUnusedImports() rule
- removed lamda fix (no longer needed)
- changed groovy target to `src/**/*.groovy`,
  because it is faster to resolve than `**/*.groovy`.
- renamed `customReplaceRegex` to its new name
  `replaceRegex`.

junit-team/junit-lambda,sbrannen/junit-lambda