Small updates to make it clear that stateless runs do not persist threads (#1706)

## Overview
Reduce confusion. Don't associate threads with stateless runs. Some
users are still getting confused by this.

## Type of change
**Type:** Update existing documentation

## Related issues/PRs
n/a

## Checklist
<!-- Put an 'x' in all boxes that apply -->
- [x] I have read the [contributing guidelines](README.md)
- [x] I have tested my changes locally using `docs dev`
- [x] All code examples have been tested and work correctly
- [x] I have used **root relative** paths for internal links
- [x] I have updated navigation in `src/docs.json` if needed

## Additional notes
n/a

Author: andrewnguonly

src/langsmith/stateless-runs.mdx

@@ -16,8 +16,6 @@ First, let's setup our client:
     client = get_client(url=<DEPLOYMENT_URL>)
     # Using the graph deployed with the name "agent"
     assistant_id = "agent"
-    # create thread
-    thread = await client.threads.create()
     ```
     </Tab>
     <Tab title="Javascript">
@@ -27,8 +25,6 @@ First, let's setup our client:
     const client = new Client({ apiUrl: <DEPLOYMENT_URL> });
     // Using the graph deployed with the name "agent"
     const assistantId = "agent";
-    // create thread
-    const thread = await client.threads.create();
     ```
     </Tab>
     <Tab title="CURL">
@@ -159,28 +155,28 @@ Output:
 
 ```
 {
-'messages': [
-{
-'content': 'Hello! My name is Bagatur and I am 26 years old.',
-'additional_kwargs': {},
-'response_metadata': {},
-'type': 'human',
-'name': None,
-'id': '5e088543-62c2-43de-9d95-6086ad7f8b48',
-'example': False}
-,
-{
-'content': "Hello Bagatur! It's nice to meet you. Thank you for introducing yourself and sharing your age. Is there anything specific you'd like to know or discuss? I'm here to help with any questions or topics you'd like to explore.",
-'additional_kwargs': {},
-'response_metadata': {},
-'type': 'ai',
-'name': None,
-'id': 'run-d6361e8d-4d4c-45bd-ba47-39520257f773',
-'example': False,
-'tool_calls': [],
-'invalid_tool_calls': [],
-'usage_metadata': None
-}
-]
+    'messages': [
+        {
+            'content': 'Hello! My name is Bagatur and I am 26 years old.',
+            'additional_kwargs': {},
+            'response_metadata': {},
+            'type': 'human',
+            'name': None,
+            'id': '5e088543-62c2-43de-9d95-6086ad7f8b48',
+            'example': False
+        },
+        {
+            'content': 'Hello Bagatur! It's nice to meet you. Thank you for introducing yourself and sharing your age. Is there anything specific you'd like to know or discuss? I'm here to help with any questions or topics you'd like to explore.',
+            'additional_kwargs': {},
+            'response_metadata': {},
+            'type': 'ai',
+            'name': None,
+            'id': 'run-d6361e8d-4d4c-45bd-ba47-39520257f773',
+            'example': False,
+            'tool_calls': [],
+            'invalid_tool_calls': [],
+            'usage_metadata': None
+        }
+    ]
 }
 ```