Change location of site-header class to temporarily avoid style collisions.

quadrat/block-templates/index.html

@@ -1,5 +1,5 @@
 <!-- wp:spacer {"height":10} -->
-<div style="height:10px" aria-hidden="true" class="wp-block-spacer"></div>
+<div style="height:10px" aria-hidden="true" class="wp-block-spacer site-header"></div>
 <!-- /wp:spacer -->
 
-<!-- wp:template-part {"area":"header","className":"site-header"} /-->
+<!-- wp:template-part {"area":"header"} /-->