Just fixing small misspelling

Small misspelling

docs/guide/bootstrap-widgets.md

@@ -54,7 +54,7 @@ Using the .less files of Bootstrap directly
 If you want to include the [Bootstrap css directly in your less files](http://getbootstrap.com/getting-started/#customizing)
 you may need to disable the original bootstrap css files to be loaded.
 You can do this by setting the css property of the [[yii\bootstrap\BootstrapAsset|BootstrapAsset]] to be empty.
-For this you need to configure the `assetManagner` application component as follows:
+For this you need to configure the `assetManager` application component as follows:
 
 ```php
     'assetManager' => [