added emphatises to phpdoc in asset bundle

framework/web/AssetManager.php

@@ -41,7 +41,7 @@ use yii\helpers\FileHelper;
 class AssetManager extends Component
 {
     /**
-     * @var array list of available asset bundles. The keys are the class names (without leading backslash)
+     * @var array list of available asset bundles. The keys are the class names (**without leading backslash**)
      * of the asset bundles, and the values are either the configuration arrays for creating the [[AssetBundle]]
      * objects or the corresponding asset bundle instances. For example, the following code disables
      * the bootstrap css file used by Bootstrap widgets (because you want to use your own styles):