Fixes #6794: incorrect docs mention of th element

docs/base-css.html

@@ -857,8 +857,7 @@ For example, <code><section></code> should be wrapped
                   <code>&lt;th&gt;</code>
                 </td>
                 <td>
-                  Special table cell for column (or row, depending on scope and placement) labels<br>
-                  Must be used within a <code>&lt;thead&gt;</code>
+                  Special table cell for column (or row, depending on scope and placement) labels
                 </td>
               </tr>
               <tr>

docs/templates/pages/base-css.mustache

@@ -794,8 +794,7 @@
                   <code>&lt;th&gt;</code>
                 </td>
                 <td>
-                  {{_i}}Special table cell for column (or row, depending on scope and placement) labels{{/i}}<br>
-                  {{_i}}Must be used within a <code>&lt;thead&gt;</code>{{/i}}
+                  {{_i}}Special table cell for column (or row, depending on scope and placement) labels{{/i}}
                 </td>
               </tr>
               <tr>