Remove unused navigation header template part. (#3970)

* Remove unused navigation header template part.

This change removes the unused navigation template part and the
reference to it from theme.json.  It also updates the navigation block
in the header template part to include responsive navigation by default
and remove unnecessary block attributes (values were either default or
expressed in theme.json).

* changed header to div to prevent double header elements in rendered page

blockbase/block-template-parts/header.html

@@ -1,6 +1,6 @@
 <!-- wp:group {"align":"full","tagName":"header","style":{"spacing":{"padding":{"right":"35px","left":"35px"}}},"className":"site-header"} -->
-<header class="wp-block-group alignfull site-header" style="padding-right:35px;padding-left:35px">
+<div class="wp-block-group alignfull site-header" style="padding-right:35px;padding-left:35px">
 	<!-- wp:site-title /-->
-	<!-- wp:navigation {"orientation":"horizontal","textColor":"foreground-light","itemsJustification":"right","fontSize":"small"} /-->
-</header>
-<!-- /wp:group -->
+	<!-- wp:navigation {"isResponsive":true} /-->
+</div>
+<!-- /wp:group -->

blockbase/block-template-parts/navigation.html

@@ -1,5 +0,0 @@
-<!-- wp:navigation {"orientation":"horizontal","itemsJustification":"center","isResponsive":true} -->
-<!-- /wp:navigation -->
-<!-- wp:spacer {"height":60} -->
-<div style="height:60px" aria-hidden="true" class="wp-block-spacer"></div>
-<!-- /wp:spacer -->

blockbase/theme.json

@@ -8,10 +8,6 @@
 		{
 			"name": "footer",
 			"area": "footer"
-		},
-		{
-			"name": "navigation",
-			"area": "navigation"
 		}
 	],
 	"settings": {