Update comment to reflect that both an annotation AND a group can be direct-linked

The URL fragment syntax for direct links only supports either an
annotation or a group, the client's JSON configuration however currently allows
both an annotation and a group to be specified. If that happens, the
client goes to the group containing the direct-linked annotation, but
will still add the direct-linked group to the groups list.

src/sidebar/services/groups.js

@@ -158,8 +158,7 @@ function groups(
    * group.
    *
    * The groups that are fetched depend on the current user, the URI of
-   * the current document, and whether any direct-links were followed (either
-   * to an annotation or group).
+   * the current document, and the direct-linked group and/or annotation.
    *
    * @return {Promise<Group[]>}
    */