[Doc] Fix mkdocs. (#785)

Signed-off-by: Alicia <115451386+congw729@users.noreply.github.com>

docs/user_guide/examples/online_serving/gradio_demo.md

@@ -1,7 +0,0 @@
-# Gradio Demo
-
-Source <https://github.com/vllm-project/vllm-omni/blob/main/examples/online_serving/gradio_demo.py>.
-
-``````py
---8<-- "examples/online_serving/gradio_demo.py"
-``````

docs/user_guide/examples/online_serving/openai_chat_completion_client_for_multimodal_generation.md

@@ -1,7 +0,0 @@
-# OpenAI Chat Completion Client For Multimodal Generation
-
-Source <https://github.com/vllm-project/vllm-omni/blob/main/examples/online_serving/openai_chat_completion_client_for_multimodal_generation.py>.
-
-``````py
---8<-- "examples/online_serving/openai_chat_completion_client_for_multimodal_generation.py"
-``````