Remove rspamd unused env var from start script

Environment variable FRONT_ADDRESS is unused in rspamd
FRONT_ADDRESS references were removed with commit 8172f3e in PR #727

core/rspamd/start.py

@@ -10,7 +10,6 @@ log.basicConfig(stream=sys.stderr, level=os.environ.get("LOG_LEVEL", "WARNING"))
 
 # Actual startup script
 
-os.environ["FRONT_ADDRESS"] = system.get_host_address_from_environment("FRONT", "front")
 os.environ["REDIS_ADDRESS"] = system.get_host_address_from_environment("REDIS", "redis")
 
 if os.environ.get("ANTIVIRUS") == 'clamav':