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

Fixing issue - #14494 to
avoid Kendra query ValidationException

<!-- Thank you for contributing to LangChain!

Replace this entire comment with:
- **Description:** Update kendra.py to avoid Kendra query
ValidationException,
- **Issue:** the issue
##14494,
  - **Dependencies:** None,
  - **Tag maintainer:** ,
  - **Twitter handle:** 

If no one reviews your PR within a few days, please @-mention one of
@baskaryan, @eyurtsev, @hwchase17.
 -->

---------

Co-authored-by: Harrison Chase <[email protected]>

libs/community/langchain_community/retrievers/kendra.py

@@ -379,7 +379,9 @@ def create_client(cls, values: Dict[str, Any]) -> Dict[str, Any]:
     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: