Update kendra.py to avoid Kendra query ValidationException (#14866)

Fixing issue - https://github.com/langchain-ai/langchain/issues/14494 to
avoid Kendra query ValidationException

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- **Description:** Update kendra.py to avoid Kendra query
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---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

libs/community/langchain_community/retrievers/kendra.py

@@ -379,7 +379,9 @@ class AmazonKendraRetriever(BaseRetriever):
     def _kendra_query(self, query: str) -> Sequence[ResultItem]:
         kendra_kwargs = {
             "IndexId": self.index_id,
-            "QueryText": query.strip(),
+            # truncate the query to ensure that
+            # there is no validation exception from Kendra.
+            "QueryText": query.strip()[0:999],
             "PageSize": self.top_k,
         }
         if self.attribute_filter is not None: