Fix the markdown rendering issue with a code block inside a markdown code block (#6625)

### Description

- Fix the markdown rendering issue with a code block inside a markdown,
using a different number of backticks for the delimiters.

Current doc site:
<https://python.langchain.com/docs/modules/data_connection/document_transformers/text_splitters/code_splitter#markdown>

After fix:
<img width="480" alt="image"
src="https://github.com/hwchase17/langchain/assets/3115235/d9921d59-64e6-4a34-9c62-79743667f528">


### Who can review

PTAL @dev2049 

Co-authored-by: Yaohui Wang <wangyaohui.01@bytedance.com>

docs/snippets/modules/data_connection/document_transformers/text_splitters/code_splitter.mdx

@@ -112,7 +112,7 @@ js_docs
 Here's an example using the Markdown text splitter.
 
 
-```python
+````python
 markdown_text = """
 # 🦜️🔗 LangChain
 
@@ -127,7 +127,7 @@ pip install langchain
 
 As an open source project in a rapidly developing field, we are extremely open to contributions.
 """
-```
+````
 
 
 ```python