fix(core): remove unnecessary role=contentinfo from page footer on login

`<footer>` has this role initially then it is a page footer, not inside `section`/`article`, and etc.

Signed-off-by: Grigorii K. Shartsev <me@shgk.me>

core/css/guest.scss

@@ -741,7 +741,7 @@ footer {
 		font-weight: bold;
 	}
 
-	&[role="contentinfo"] {
+	&.guest-box {
 		padding: 6px 24px;
 		margin-bottom: 1rem;
 

core/templates/layout.guest.php

@@ -47,7 +47,7 @@ p($theme->getTitle());
 				</main>
 			</div>
 		</div>
-		<footer role="contentinfo" class="guest-box">
+		<footer class="guest-box">
 			<p class="info">
 				<?php print_unescaped($theme->getLongFooter()); ?>
 			</p>