Update crowdsec-firewall-bouncer to latest upstream release version 0.0.21

Makefile rework
- use tagged version for download

Fixes
- set API_KEY in firewall bouncer config file

Signed-off-by: Kerma Gérald <gandalf@gk2.net>

Remove un-necessary crowdsec package dependency, to be able to use
crowdsec-firewall-bouncer independently from crowdsec local installation.
(with remote API)

Fix issue: https://github.com/openwrt/packages/issues/17406

Description:
  using crowdsec-firewall-bouncer on many OpenWRT devices connected
  with my domain LAPI server (which collect many crowdsec machines,
  mostly nginx), it works great. Actually, crowdsec package is not
  mandatory for that usage, it would be great if it was not a dependency.

Signed-off-by: Kerma Gérald <gandalf@gk2.net>

Update to upstream release 0.0.18

Signed-off-by: Kerma Gérald <gandalf@gk2.net>

crowdsec-firewall-boucer: update to 0.0.16

Signed-off-by: Kerma Gérald <gandalf@gk2.net>

/net/crowdsec-firewall-bouncer/

crowdsec-firewall-bouncer will fetch new and old decisions from
 a CrowdSec API to add them in a blocklist used by supported firewalls.

Signed-off-by: Kerma Gérald <gandalf@gk2.net>