Update README.md (#377)

fixing wrong link in README.MD

Author: davidsbatista

README.md

@@ -67,7 +67,7 @@ that includes it. Once it reaches the end of its lifespan, the experiment will b
 [12]: https://github.com/deepset-ai/haystack-experimental/discussions/364
 [13]: https://github.com/deepset-ai/haystack-experimental/blob/main/haystack_experimental/components/retrievers/multi_query_embedding_retriever.py
 [14]: https://github.com/deepset-ai/haystack-experimental/blob/main/haystack_experimental/components/retrievers/multi_query_text_retriever.py
-[15]: https://github.com/deepset-ai/haystack-experimental/blob/main/haystack_experimental/components/retrievers/md_header_level_inferrer.py
+[15]: https://github.com/deepset-ai/haystack-experimental/blob/main/haystack_experimental/components/preprocessors/md_header_level_inferrer.py      
 [16]: https://github.com/deepset-ai/haystack-experimental/discussions/376