config: Move NFT_COUNTER into conditional
The option has been removed and is now always enabled with nftables core.
See also https://git.kernel.org/torvalds/c/023223d
Seems to work fine with the rc1 suffix, tested by changing to ">=3.13.0 <5.18_rc1"
and kconfig check fails. With this change kconfig check works on an 5.17_rc5 kernel.