Update column type for MySQL sessions table

Author: beejaz

session/database.rst

@@ -389,7 +389,7 @@ MySQL
     CREATE TABLE `sessions` (
         `sess_id` VARBINARY(128) NOT NULL PRIMARY KEY,
         `sess_data` BLOB NOT NULL,
-        `sess_lifetime` MEDIUMINT NOT NULL,
+        `sess_lifetime` INTEGER UNSIGNED NOT NULL,
         `sess_time` INTEGER UNSIGNED NOT NULL
     ) COLLATE utf8mb4_bin, ENGINE = InnoDB;