ip2cc_uninstall needs to drop table

One of the critical fixes between 6.x-1.0-beta1 and 6.x-1.x-dev is the fixing of the char fields in the database, which were mistakenly defaulted to 1 char, rather than 2.

However ip2cc_uninstall() does not specify the dropping of the ip2cc table upon uninstallation so upgrading from beta1 to dev does not fix the error as the ip2cc data is just inserted into same truncated table columns.