You can uninstall or removes an installed iptables-nftables-compat package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove iptables-nftables-compat
If you would like to remove iptables-nftables-compat and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove iptables-nftables-compat
If you use with purge options to iptables-nftables-compat package all the configuration and dependent packages will be removed.
$ sudo apt-get purge iptables-nftables-compat
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove iptables-nftables-compat