roles/common: adjust update-firehol-nftables.service

This service does not actually depend on nftables, at least not in
the systemd sense of dependency. Furthermore, this hard dependency
was causing the service to fail when it restarts nftables at the
end, which causes systemd to start it again and again until it hits
a restarting too quickly error.

roles/common/files/update-firehol-nftables.service

@@ -1,10 +1,7 @@
 [Unit]
 Description=Update FireHOL lists
-# This service will fail if nftables is not running so we use Requires to make
-# sure that nftables is started.
-Requires=nftables.service
-# Make sure the network is up and nftables is started
-After=network-online.target nftables.service
+# Make sure the network is up
+After=network-online.target
 Wants=network-online.target update-firehol-nftables.timer
 
 [Service]