Docs: exporting created knowledge graphs is not supported (#8465)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [x] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

docs/guides/dataset/construct_knowledge_graph.md

@@ -93,4 +93,8 @@ To remove the generated knowledge graph, delete all related files in your knowle
 
 ### Where is the created knowledge graph stored?
 
-All chunks of the created knowledge graph are stored in RAGFlow's document engine: either Elasticsearch or [Infinity](https://github.com/infiniflow/infinity).
+All chunks of the created knowledge graph are stored in RAGFlow's document engine: either Elasticsearch or [Infinity](https://github.com/infiniflow/infinity).
+
+### How to export a created knowledge graph?
+
+Nope. Exporting a created knowledge graph is not supported. If you still consider this feature essential, please [raise an issue](https://github.com/infiniflow/ragflow/issues) explaining your use case and its importance.

docs/references/http_api_reference.md

@@ -3226,7 +3226,9 @@ Failure:
 
 Generates five to ten alternative question strings from the user's original query to retrieve more relevant search results.
 
-This operation requires a `Bearer Login Token`, which typically expires with in 24 hours. You can find the it in the Request Headers in your browser easily.
+This operation requires a `Bearer Login Token`, which typically expires with in 24 hours. You can find the it in the Request Headers in your browser easily as shown below:
+
+![Image](https://github.com/user-attachments/assets/17a5a0fe-e411-4e35-8251-85c71444468b)
 
 :::tip NOTE
 The chat model autonomously determines the number of questions to generate based on the instruction, typically between five and ten.