Follow up 2d53a78:

* Added 'bonus2 bAddItemGroupHealRate' to replace 'bonus2 bAddItemHealRate' for Item Group ID usage. Since MAX_ITEMGROUP is removed, there is no identifier which entry that Item ID or Item Group. Previous check using 'if (type2 < MAX_ITEMGROUP)' (https://github.com/rathena/rathena/commit/2d53a782fad395b648c2a5e1ac5e983c43fe45a0#diff-08420bab8271f3965304fee42cf4b865L3220)
* bonus2 bAddItemHealRate,iid,n;
* bonus2 bAddItemGroupHealRate,ig,n;

Signed-off-by: Cydh Ramdh <house.bad@gmail.com>