docs: langchain-ai21 update ai21 docs (#28076)

Thank you for contributing to LangChain!

Update docs to match latest langchain-ai21 release.

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

docs/docs/integrations/llms/ai21.ipynb

@@ -17,6 +17,9 @@
    "source": [
     "# AI21LLM\n",
     "\n",
+    ":::caution This service is deprecated.\n",
+    "See [this page](https://python.langchain.com/docs/integrations/chat/ai21/) for the updated ChatAI21 object. :::\n",
+    "\n",
     "This example goes over how to use LangChain to interact with `AI21` Jurassic models. To use the Jamba model, use the [ChatAI21 object](https://python.langchain.com/docs/integrations/chat/ai21/) instead.\n",
     "\n",
     "[See a full list of AI21 models and tools on LangChain.](https://pypi.org/project/langchain-ai21/)\n",

docs/docs/integrations/providers/ai21.mdx

@@ -15,26 +15,6 @@ This page covers how to use the `AI21` ecosystem within `LangChain`.
 pip install langchain-ai21
 ```
 
-## LLMs
-
-See a [usage example](/docs/integrations/llms/ai21).
-
-### AI21 LLM
-
-```python
-from langchain_ai21 import AI21LLM
-```
-
-### AI21 Contextual Answer
-
-You can use AI21’s contextual answers model to receive text or document, 
-serving as a context, and a question and return an answer based entirely on this context.
-
-```python
-from langchain_ai21 import AI21ContextualAnswers
-```
-
-
 ## Chat models
 
 ### AI21 Chat 
@@ -45,23 +25,32 @@ See a [usage example](/docs/integrations/chat/ai21).
 from langchain_ai21 import ChatAI21
 ```
 
-## Embedding models
+## Deprecated features
+
+:::caution The following features are deprecated. 
+:::
+
+### AI21 LLM
+
+```python
+from langchain_ai21 import AI21LLM
+```
+
+### AI21 Contextual Answer
+
+```python
+from langchain_ai21 import AI21ContextualAnswers
+```
 
 ### AI21 Embeddings
 
-See a [usage example](/docs/integrations/text_embedding/ai21).
-
 ```python
 from langchain_ai21 import AI21Embeddings
 ```
-
 ## Text splitters
 
 ### AI21 Semantic Text Splitter
 
-See a [usage example](/docs/integrations/document_transformers/ai21_semantic_text_splitter).
-
 ```python
 from langchain_ai21 import AI21SemanticTextSplitter
 ```
-

docs/docs/integrations/text_embedding/ai21.ipynb

@@ -17,6 +17,8 @@
    "source": [
     "# AI21Embeddings\n",
     "\n",
+    ":::caution This service is deprecated. :::\n",
+    "\n",
     "This will help you get started with AI21 embedding models using LangChain. For detailed documentation on `AI21Embeddings` features and configuration options, please refer to the [API reference](https://python.langchain.com/api_reference/ai21/embeddings/langchain_ai21.embeddings.AI21Embeddings.html).\n",
     "\n",
     "## Overview\n",