fix(docs): fix player configuration code in drm config tutorial (shak…

…a-project#5359)

This PR updates the DRM configuration tutorial.

The configuration code example is incorrect, and also it suggests you
can change the mapping, which is not true, you are only able to
overwrite parts of it.

Co-authored-by: Ivan Kohut <ivan.kohut@lamin.ar>

docs/tutorials/drm-config.md

@@ -59,15 +59,18 @@ If this is the only `<ContentProtection>` element in the manifest, Shaka will
 try all key systems it knows. (Based on keySystemsByURI in
 {@linksource shaka.extern.DashManifestConfiguration}.)
 
-Through `player.configure()`, you can change the dash key systems mapping by
+Through `player.configure()`, you can update the dash key systems mapping by
 scheme URI:
+
 ```js
 player.configure({
-  dash: {
-    keySystemsByURI: {
-      'urn:uuid:9a04f079-9840-4286-ab92-e65be0885f95': 'com.microsoft.playready.recommendation',
-      'urn:uuid:79f0049a-4098-8642-ab92-e65be0885f95': 'com.microsoft.playready.recommendation',
-    }
+  manifest: {
+    dash: {
+      keySystemsByURI: {
+        'urn:uuid:9a04f079-9840-4286-ab92-e65be0885f95': 'com.microsoft.playready.recommendation',
+        'urn:uuid:79f0049a-4098-8642-ab92-e65be0885f95': 'com.microsoft.playready.recommendation',
+      }
+  }
   }
 });
 ```