MDL-31494 fix link to adodb driver docs

target="_bank" is valid again in html5, it does help a lot here no matter what legacy accessibility guides say…

auth/db/lang/en/auth_db.php

@@ -57,7 +57,7 @@
 $string['auth_dbsybasequotinghelp'] = 'Sybase style single quote escaping - needed for Oracle, MS SQL and some other databases. Do not use for MySQL!';
 $string['auth_dbtable'] = 'Name of the table in the database';
 $string['auth_dbtable_key'] = 'Table';
-$string['auth_dbtype'] = 'The database type (See the <a href="../lib/adodb/readme.htm#drivers">ADOdb documentation</a> for details)';
+$string['auth_dbtype'] = 'The database type (See the <a href="http://phplens.com/adodb/supported.databases.html" target="_blank">ADOdb documentation</a> for details)';
 $string['auth_dbtype_key'] = 'Database';
 $string['auth_dbupdatinguser'] = 'Updating user {$a->name} id {$a->id}';
 $string['auth_dbuser'] = 'Username with read access to the database';