Fixes DB admin ranks being 16 bits wide instead of 24 (#89348)

## About The Pull Request
smallint is 2 bytes, increased it to mediumint which is 3 bytes
Issue has not cropped up yet as theres only 15 flags right now, but
there can be up to 24 in dm side soooo

```
DEBUG-SQL: MySqlError { ERROR 1264 (22003): Out of range value for column 'flags' at row 1 } | Query used: INSERT INTO admin_ranks
 - (rank, flags, exclude_flags, can_edit_flags)
```


my mysql is broken so I havent tested the update query but how bad can
it be :clueless:
## Changelog
🆑
server: An issue where more than 16 admin flags could not exist in the
DB has been corrected
/🆑

---------

Co-authored-by: TiviPlus <572233640+TiviPlus@users.noreply.com>

SQL/tgstation_schema_prefixed.sql

@@ -53,9 +53,9 @@ DROP TABLE IF EXISTS `SS13_admin_ranks`;
 /*!40101 SET character_set_client = utf8 */;
 CREATE TABLE `SS13_admin_ranks` (
   `rank` varchar(32) NOT NULL,
-  `flags` smallint(5) unsigned NOT NULL,
-  `exclude_flags` smallint(5) unsigned NOT NULL,
-  `can_edit_flags` smallint(5) unsigned NOT NULL,
+  `flags` mediumint(5) unsigned NOT NULL,
+  `exclude_flags` mediumint(5) unsigned NOT NULL,
+  `can_edit_flags` mediumint(5) unsigned NOT NULL,
   PRIMARY KEY (`rank`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
 /*!40101 SET character_set_client = @saved_cs_client */;