Revert "Add upgrade class for data migration"

This reverts commit e6245be4a3.

admin/core/packages/1.3.39.php

@@ -1,27 +0,0 @@
-<?php 
-	
-	// If this file is called directly, abort.
-	if ( ! defined( 'WPINC' ) ) {
-		die;
-	}
-
-	/**
-  	 * This populates all existing UM users with meta_key `last_login` as `user_registered` if the meta key doesn't exist.
-  	 * Target Version: 1.3.39
-  	 */
-  	
-	global $wpdb, $ultimatemember;
-  	$wpdb->query('INSERT INTO '.$wpdb->usermeta.'(user_id, meta_key, meta_value) 
-	   			SELECT uu.ID, "_um_last_login", uu.user_registered
-	   				FROM '.$wpdb->users.' AS uu
-	   			WHERE 
-	   				uu.ID NOT IN(
-	   						SELECT user_id FROM '.$wpdb->usermeta.' 
-	      					WHERE meta_key = "_um_last_login" 
-	      					GROUP BY user_id
-	      			)'
-  	);
-
-
-
- ?>