Update README.md to match defaults in inspector

When launching inspector and changing to use SSE, the URL is set to `http://localhost:3001/sse`. It's quite confusing to have an example use different endpoint names and port, hence the change.

Author: ihrpr

README.md

@@ -224,7 +224,7 @@ const server = new McpServer({
 
 const app = express();
 
-app.get("/mcp", async (req, res) => {
+app.get("/sse", async (req, res) => {
   const transport = new SSEServerTransport("/messages", res);
   await server.connect(transport);
 });
@@ -236,7 +236,7 @@ app.post("/messages", async (req, res) => {
   await transport.handlePostMessage(req, res);
 });
 
-app.listen(3000);
+app.listen(3001);
 ```
 
 ### Testing and Debugging