Theme: Switch to overlayMenu to restore menu design.

`isResponsive` was removed in WordPress/gutenberg#35568, which broke several parts of the design.

Similar changes were made in a corresponding commit to the global header/footer.

Fixes #53

source/wp-content/themes/wporg-news-2021/block-template-parts/local-navigation.html

@@ -2,7 +2,7 @@
 <div class="wp-block-group alignfull local-header__navigation">
 	<!-- wp:group {"className":"local-header__breadcrumb"} -->
 	<div class="wp-block-group local-header__breadcrumb">
-		<!-- wp:navigation {"orientation":"horizontal"} -->
+		<!-- wp:navigation {"orientation":"horizontal","overlayMenu":"never"} -->
 			<!-- wp:home-link {"label":"News"} /-->
 		<!-- /wp:navigation -->
 		<!-- wp:query-title {"type":"archive","className":"local-header__breadcrumb-current"} /-->