remove nested .bd-example

docs/components/buttons.md

@@ -169,8 +169,7 @@ The checked state for these buttons is **only updated via `click` event** on the
 Note that pre-checked buttons require you to manually add the `.active` class to the input's `<label>`.
 
 {% example html %}
-<div class="bd-example">
-  <div class="btn-group" data-toggle="buttons">
+<div class="btn-group" data-toggle="buttons">
   <label class="btn btn-primary active">
     <input type="checkbox" checked autocomplete="off"> Checkbox 1 (pre-checked)
   </label>
@@ -180,7 +179,6 @@ Note that pre-checked buttons require you to manually add the `.active` class to
   <label class="btn btn-primary">
     <input type="checkbox" autocomplete="off"> Checkbox 3
   </label>
-  </div>
 </div>
 {% endexample %}