docs: Doc update for LocalizedSettings images to not allow URLs to ex…

…ternal image sources.

PiperOrigin-RevId: 355683554

google/actions/sdk/v2/theme_customization.proto

@@ -69,15 +69,15 @@ message ThemeCustomization {
   // This should be specified as a reference to the corresponding image in the
   // `resources/images/` directory. Eg: `$resources.images.foo` (without the
   // extension) for image in `resources/images/foo.jpg`
-  // When working on a project pulled from Console the Google managed url pulled
-  // could be used.
+  // When working on a project pulled from Console, the Google-managed URL
+  // pulled could be used. URLs from external sources are not allowed.
   string landscape_background_image = 5;
 
   // Portrait mode (minimum 1200x1920 pixels).
   // This should be specified as a reference to the corresponding image in the
   // `resources/images/` directory. Eg: `$resources.images.foo` (without the
   // extension) for image in `resources/images/foo.jpg`
-  // When working on a project pulled from Console the Google managed url pulled
-  // could be used.
+  // When working on a project pulled from Console, the Google-managed URL
+  // pulled could be used. URLs from external sources are not allowed.
   string portrait_background_image = 6;
 }