URL for list tools test needs /mcp

**MCP-SERVER-HELLO-WORLD**

In the simple test script to list tools on the README.md file, the URL should have /mcp on the end to verify connectivity to the server.

https://github.com/databricks/app-templates/tree/main/mcp-server-hello-world#end-to-end-test-your-locally-running-mcp-server

ie http://localhost:8000 needs to be http://localhost:8000/mcp