document that fieldset[disabled] is somewhat broken in IE11; fixes #14509

docs/_includes/css/forms.html

@@ -469,7 +469,7 @@
 
   <div class="bs-callout bs-callout-danger">
     <h4>Cross-browser compatibility</h4>
-    <p>While Bootstrap will apply these styles in all browsers, Internet Explorer 9 and below don't actually support the <code>disabled</code> attribute on a <code>&lt;fieldset&gt;</code>. Use custom JavaScript to disable the fieldset in these browsers.</p>
+    <p>While Bootstrap will apply these styles in all browsers, Internet Explorer 11 and below don't fully support the <code>disabled</code> attribute on a <code>&lt;fieldset&gt;</code>. Use custom JavaScript to disable the fieldset in these browsers.</p>
   </div>
 
   <div class="bs-example">