community[patch]: Fix MongoDBAtlasVectorSearch max_marginal_relevance…

…_search (#17971)

Description:
* `self._embedding_key` is accessed after deletion, breaking
`max_marginal_relevance_search` search
* Introduced in:
e135e52
* Updated but still persists in:
ce22e10

Issue: #17963

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/vectorstores/mongodb_atlas.py

@@ -215,7 +215,6 @@ def _similarity_search_with_score(
         for res in cursor:
             text = res.pop(self._text_key)
             score = res.pop("score")
-            del res[self._embedding_key]
             docs.append((Document(page_content=text, metadata=res), score))
         return docs