chore: replace image

Author: tianzhou

docs/blog/postgres-mcp-server-review-dbhub.mdx

@@ -160,7 +160,7 @@ DBHub includes a [built-in web interface](/workbench/overview) with two main fea
 
 1. **Tool Execution**: Run database tools directly from your browser—useful for testing and debugging without an MCP client. Custom tools render as constrained forms with validated inputs.
 
-    ![workbench](https://raw.githubusercontent.com/bytebase/dbhub/main/docs/images/workbench/workbench.webp)
+    ![workbench](https://raw.githubusercontent.com/bytebase/dbhub/main/docs/images/workbench/custom-tool.webp)
 
 1. **Request Traces**: Inspect MCP requests to understand how AI agents interact with DBHub.