Docs: Update image_rendering.md (#22586)

Trying to fix the numbering in Run as standalone Node.js application.

docs/sources/administration/image_rendering.md

@@ -89,11 +89,13 @@ The following example describes how to build and run the remote HTTP rendering s
     yarn install --pure-lockfile
     yarn run build
     ```
-3. Run the server
+
+3. Run the server:
 
     ```bash
     node build/app.js server --port=8081
     ```
+
 4. Update Grafana configuration:
 
     ```
@@ -101,6 +103,7 @@ node build/app.js server --port=8081
     server_url = http://localhost:8081/render
     callback_url = http://localhost:3000/
     ```
+
 5. Restart Grafana.
 
 ## PhantomJS