Change header to use markdown (#21809)

Header will now display in the Contents section.

diff --git a/docs/layout/responsive-utilities.md b/docs/layout/responsive-utilities.md
index c3f0c00901b9f82c79f7f65037908555d1e60bea..fdea34bd957ce7cbbe6dc374868f32cf62157551 100644 (file)
--- a/docs/layout/responsive-utilities.md
+++ b/docs/layout/responsive-utilities.md
@@ -132,7 +132,8 @@ Try to use these on a limited basis and avoid creating entirely different versio
   </tbody>
 </table>
 
-<h2 id="responsive-utilities-print">Print classes</h2>
+## Print classes
+
 <p>Similar to the regular responsive classes, use these for toggling content for print.</p>
 <table class="table table-bordered table-striped responsive-utilities table-responsive">
   <thead>