Removed the bits that disabled the navigation fallback so that navigation would work as expected. (#6743)

blockbase/functions.php

@@ -119,14 +119,6 @@ add_action(
 	}
 );
 
-/**
- * Disable the fallback for the core/navigation block.
- */
-function blockbase_core_navigation_render_fallback() {
-	return null;
-}
-add_filter( 'block_core_navigation_render_fallback', 'blockbase_core_navigation_render_fallback' );
-
 /**
  * Block Patterns.
  */