Whenever you installed that extension, a new catalog-product-eav-attribute
brand_id has created by the installer script of that extension.
Now you removed the code of this module and erased all assoicated tables. But you forgot to remove the attribute
brand_id from the eav-attribute-table
brand_id is of type select-attribute.So most probably it uses a source-model for this attribute which is normally used to specify the options and labels of that attribute. Since you have removed the code, the attribute can't find it's source model and hence you are getting this error.
So to avoid this, you need to completely remove the attribute
brand_id. Use this :
DELETE FROM `eav_attribute` WHERE `attribute_code` = 'brand_id';