err how?
still present in the latest current release, so not sure what you are on about
actually that is a legacy command, iptable_mangle is loaded by default now and has been for a while (number of months if not years), so if its a security concern you best take that up with limetech 😛 - issue command lsmod and note the following:-
root@Tower:~# lsmod | grep 'iptable_mangle'
iptable_mangle 16384 2
ip_tables 28672 8 iptable_filter,iptable_raw,iptable_nat,iptable_mangle
x_tables 28672 17 ip6table_filter,xt_conntrack,iptable_filter,xt_tcpudp,xt_addrtype,xt_CHECKSUM,xt_nat,xt_comment,ip6_tables,ipt_REJECT,xt_connmark,iptable_raw,ip_tables,ip6table_mangle,xt_MASQUERADE,iptable_mangle,xt_mark