[Documentation] Switch Step 1 to fenced

docs/src/tutorials/index.md

@@ -2346,6 +2346,7 @@ add a top-level object which will serve as a container; in the next step, we
 will populate this with the contents of the telemetry dictionary (which we 
 will retrieve from the server.)
 
+```diff
 define([
     'legacyRegistry'
 ], function (
@@ -2375,6 +2376,7 @@ will retrieve from the server.)
         }
     });
 });
+```
 __tutorials/telemetry/bundle.js__
 
 Here, we've created our initial telemetry plugin. This exposes a new domain