docs: fixed nimble's provider page and retriever (#29695)

## **Description:**
- Added information about the retriever that Nimble's provider exposes.
- Fixed the authentication explanation on the retriever page.

docs/docs/integrations/providers/nimble.ipynb

@@ -27,18 +27,12 @@
     "If you'd like to learn more about Nimble, visit us at [nimbleway.com](https://www.nimbleway.com/).\n",
     "\n",
     "\n",
-    "## Currently we expose the following components\n",
+    "## Retrievers:"
-    "\n",
-    "*   **Retriever** - Allow us to query the internet and get parsed textual results utilizing several search engines.\n",
-    "\n",
-    "\n"
    ]
   },
   {
    "cell_type": "markdown",
-   "source": [
+   "source": "### NimbleSearchRetriever",
-    "## Usage"
-   ],
    "metadata": {
     "id": "AuMFgVFrKbNH"
    },
@@ -47,7 +41,9 @@
   {
    "cell_type": "markdown",
    "source": [
-    "In order to use our provider you have to provide an API key like so"
+    "Enables developers to build RAG applications and AI Agents that can search, access, and retrieve online information from anywhere on the web.\n",
+    "\n",
+    "We need to install the `langchain-nimble` python package."
    ],
    "metadata": {
     "id": "sFlPjZX9KdK6"
@@ -55,25 +51,32 @@
    "id": "sFlPjZX9KdK6"
   },
   {
+   "metadata": {},
    "cell_type": "code",
-   "source": [
+   "outputs": [],
-    "import getpass\n",
-    "import os\n",
-    "\n",
-    "os.environ[\"NIMBLE_API_KEY\"] = getpass.getpass()"
-   ],
-   "metadata": {
-    "id": "eAqSHZ-Z8R3F"
-   },
-   "id": "eAqSHZ-Z8R3F",
    "execution_count": null,
-   "outputs": []
+   "source": "%pip install -U langchain-nimble",
+   "id": "65f237c852aa3885"
+  },
+  {
+   "metadata": {},
+   "cell_type": "markdown",
+   "source": "See a [usage example](/docs/integrations/retrievers/nimble/).",
+   "id": "77bd7b9a6a8e381b"
+  },
+  {
+   "metadata": {},
+   "cell_type": "markdown",
+   "source": [
+    "```python\n",
+    "from langchain_nimble import NimbeSearchRetriever\n",
+    "```"
+   ],
+   "id": "511f9d569c21a5d2"
   },
   {
    "cell_type": "markdown",
-   "source": [
+   "source": "Note that authentication is required, please refer to the [Setup section in the documentation](/docs/integrations/retrievers/nimble/#setup).",
-    "For more information about the Authentication process, see [Nimble APIs Authentication Documentation](https://docs.nimbleway.com/nimble-sdk/web-api/nimble-web-api-quick-start-guide/nimble-apis-authentication)."
-   ],
    "metadata": {
     "id": "WfwnI_RS8PO5"
    },