[Fix bug] The adaptation for rewrite_invalid_question_prompt was not saved (#1071)

*Changes:*
- Added saving of prompt adaptation.

Author: psydok

src/ragas/testset/evolutions.py

@@ -276,6 +276,7 @@ def save(self, cache_dir: t.Optional[str] = None) -> None:
         assert self.question_filter is not None, "question_filter cannot be None"
         self.question_answer_prompt.save(cache_dir)
         self.find_relevant_context_prompt.save(cache_dir)
+        self.rewrite_invalid_question_prompt.save(cache_dir)
         self.node_filter.save(cache_dir)
         self.question_filter.save(cache_dir)