Kendra retriever api (#6616)

## Description
Replaces [Kendra
Retriever](https://github.com/hwchase17/langchain/blob/master/langchain/retrievers/aws_kendra_index_retriever.py)
with an updated version that uses the new [retriever
API](https://docs.aws.amazon.com/kendra/latest/dg/searching-retrieve.html)
which is better suited for retrieval augmented generation (RAG) systems.

**Note**: This change requires the latest version (1.26.159) of boto3 to
work. `pip install -U boto3` to upgrade the boto3 version.

cc @hupe1980
cc @dev2049

docs/extras/modules/data_connection/retrievers/integrations/amazon_kendra_retriever.ipynb

@@ -26,7 +26,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "#!pip install boto3"
+    "%pip install boto3"
    ]
   },
   {
@@ -36,7 +36,7 @@
    "outputs": [],
    "source": [
     "import boto3\n",
-    "from langchain.retrievers import AwsKendraIndexRetriever"
+    "from langchain.retrievers import AmazonKendraRetriever"
    ]
   },
   {
@@ -53,11 +53,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "kclient = boto3.client(\"kendra\", region_name=\"us-east-1\")\n",
-    "\n",
-    "retriever = AwsKendraIndexRetriever(\n",
-    "    kclient=kclient,\n",
-    "    kendraindex=\"kendraindex\",\n",
+    "retriever = AmazonKendraRetriever(\n",
+    "    index_id=\"c0806df7-e76b-4bce-9b5c-d5582f6b1a03\"\n",
     ")"
    ]
   },
@@ -66,7 +63,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Now you can use retrieved documents from AWS Kendra Index"
+    "Now you can use retrieved documents from Kendra index"
    ]
   },
   {