Twenty Twenty-One: Add a missing HTML comment for Customizer notice control.

This brings consistency with other bundled themes, like Twenty Nineteen.

Props haritpanchal.
Fixes #55725.


git-svn-id: https://develop.svn.wordpress.org/trunk@54221 602fd350-edb4-49c9-b593-d223f7449a82

Author: audrasjb

src/wp-content/themes/twentytwentyone/classes/class-twenty-twenty-one-customize-notice-control.php

@@ -40,7 +40,7 @@ public function render_content() {
 			<p><a href="<?php echo esc_url( __( 'https://wordpress.org/support/article/twenty-twenty-one/#dark-mode-support', 'twentytwentyone' ) ); ?>">
 				<?php esc_html_e( 'Learn more about Dark Mode.', 'twentytwentyone' ); ?>
 			</a></p>
-		</div>
+		</div><!-- .notice -->
 		<?php
 	}
 }