docs(create_sql_agent): fix reStructured Text Markup (#28356)
- **Description:** Lines of code must be indented beneath `..
code-block::` for proper formatting.
https://devguide.python.org/documentation/markup/#showing-code-examples
- **Issue:** The example code block on the `create_sql_agent` document
page is not properly rendered.
https://python.langchain.com/api_reference/community/agent_toolkits/langchain_community.agent_toolkits.sql.base.create_sql_agent.html#langchain_community.agent_toolkits.sql.base.create_sql_agent
<img width="933" alt="image"
src="https://github.com/user-attachments/assets/d764bcad-e412-408b-ab0b-9a78a11188ee">
