Update `$_old_files` for 5.7.

Follow up to [50066].

Props desrosj.
Reviewed by davidbaumwald, SergeyBiryukov.
Fixes #52334.
Built from https://develop.svn.wordpress.org/branches/5.7@50511


git-svn-id: http://core.svn.wordpress.org/branches/5.7@50124 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update-core.php

@@ -801,6 +801,8 @@ $_old_files = array(
 	// 5.6
 	'wp-includes/js/jquery/ui/position.min.js',
 	'wp-includes/js/jquery/ui/widget.min.js',
+	// 5.7
+	'wp-includes/blocks/classic/block.json',
 );
 
 /**

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-RC3-50509';
+$wp_version = '5.7-RC3-50511';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.