Update badge.mdx

Author: jancurn

sources/platform/actors/publishing/badge.mdx

@@ -25,7 +25,7 @@ This is how such a badge looks in a GitHub repository README:
 The Badge is a dynamic SVG image loaded from the Apify platform. The Badge is served from the URL Template:
 
 ```text
-https://apify.com/actor-badge?actor=:username/:actor-name
+https://apify.com/actor-badge?actor=<USERNAME>/<ACTOR>
 ```
 
 In order to embed the badge in the HTML documentation, just use it as an image wrapped in a link as shown in the example below. Don't froget to use the `username` and `actor-name` of your Actor.