Migrate to ksp 2

[ZemtsovVU]

Dependency versions were updated and migration to KSP2 was performed.

kotlinpoet now includes code like this

// FunSpec.kt

if (returnType != UNIT || emitUnitReturnType()) {
  codeWriter.emitCode(": %T", returnType)
}

/**
 * Returns whether [Unit] should be emitted as the return type.
 *
 * [Unit] is emitted as return type on a function only if it is an expression body.
 */
private fun emitUnitReturnType(): Boolean {
  if (isConstructor) {
    return false
  }
  if (name == GETTER || name == SETTER) {
    // Getter/setters don't emit return types
    return false
  }

  return body.asExpressionBody() != null
}

accordingly, I had to remove the explicit Unit type as function return type.

[outadoc]

Looks good, thank you for your contribution @ZemtsovVU! 🎉