MDEV-22630 mysql_upgrade (MariaDB 5.2.X --> MariaDB 10.3.X) does not fix...

MDEV-22630 mysql_upgrade (MariaDB 5.2.X --> MariaDB 10.3.X) does not fix auth_string to change it to authentication_string

cherry-pick from 10.4:

  commit b976b9bf
  Author: Sergei Golubchik <serg@mariadb.com>
  Date:   Tue Apr 21 18:40:15 2020 +0200

    MDEV-21244 mysql_upgrade creating empty global_priv table

    support upgrades from 5.2 privilege tables

scripts/mysql_system_tables_fix.sql

@@ -646,6 +646,7 @@ UPDATE user SET Create_tablespace_priv = Super_priv WHERE @hadCreateTablespacePr
 
 ALTER TABLE user ADD plugin char(64) CHARACTER SET latin1 DEFAULT '' NOT NULL AFTER max_user_connections,
                  ADD authentication_string TEXT NOT NULL AFTER plugin;
+ALTER TABLE user CHANGE auth_string authentication_string TEXT NOT NULL;
 ALTER TABLE user MODIFY plugin char(64) CHARACTER SET latin1 DEFAULT '' NOT NULL,
                  MODIFY authentication_string TEXT NOT NULL;
 ALTER TABLE user ADD password_expired ENUM('N', 'Y') COLLATE utf8_general_ci DEFAULT 'N' NOT NULL AFTER authentication_string;