community[patch]: Update arxiv.py with Entry ID as a return value (#14915)

Added Entry ID as a return value inside get_summaries_as_docs

- **Description:** Added the Entry ID as a return, so it's easier to
track the IDs of the papers that are being returned.


With the addition return of the entry ID in functions like
ArxivRetriever, it will be easier to reference the ID of the paper
itself.

libs/community/langchain_community/utilities/arxiv.py

@@ -118,6 +118,7 @@ class ArxivAPIWrapper(BaseModel):
             Document(
                 page_content=result.summary,
                 metadata={
+                    "Entry ID": result.entry_id,
                     "Published": result.updated.date(),
                     "Title": result.title,
                     "Authors": ", ".join(a.name for a in result.authors),