Database: Add ANSI to the list of incompatible SQL modes.

Starting with MySQL 5.7.5, the `ANSI` mode implies `ONLY_FULL_GROUP_BY`, which is already listed in `wpdb` as incompatible per [27072].

When `ANSI` is enabled on MySQL 5.7.5+, `ONLY_FULL_GROUP_BY` remains enabled even after being "unset" by `wpdb::set_sql_mode()`.

To prevent this, the `ANSI` mode should also be listed as incompatible. It is not enabled on default MySQL installations.

Props jnylen0.
Fixes #48377.

git-svn-id: https://develop.svn.wordpress.org/trunk@47171 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/wp-db.php

@@ -568,6 +568,7 @@ class wpdb {
 		'STRICT_TRANS_TABLES',
 		'STRICT_ALL_TABLES',
 		'TRADITIONAL',
+		'ANSI',
 	);
 
 	/**