Post: Remove unused variable $hidden_inputs

Author: Soean

src/wp-admin/includes/post.php

@@ -2564,7 +2564,6 @@ function the_block_editor_meta_box_post_form_hidden_fields( $post ) {
 	$classic_output = ob_get_clean();
 
 	$classic_elements = wp_html_split( $classic_output );
-	$hidden_inputs    = '';
 	foreach ( $classic_elements as $element ) {
 		if ( ! str_starts_with( $element, '<input ' ) ) {
 			continue;