Docs: remove extraneous params from block_type_metadata hook (#34151)

The `block_type_metadata` hook only accepts one argument, so the doc showing `add_filter( 'block_type_metadata', 'filter_metadata_registration', 10, 2 );` confused me. I checked the source of the filter on trac to make sure: https://core.trac.wordpress.org/browser/tags/5.8/src/wp-includes/blocks.php#L215

docs/reference-guides/filters/block-filters.md

@@ -23,7 +23,7 @@ function filter_metadata_registration( $metadata ) {
 	$metadata['apiVersion'] = 1;
 	return $metadata;
 };
-add_filter( 'block_type_metadata', 'filter_metadata_registration', 10, 2 );
+add_filter( 'block_type_metadata', 'filter_metadata_registration' );
 
 register_block_type( __DIR__ );
 ```