Report receiver: don't log senders' addresses

The rate limit keeps addresses in memory, for at most a day; the log
lines don't need them, so the privacy policy can say they aren't stored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/report-receiver/receiver.py

@@ -332,7 +332,8 @@ def make_handler(store, limiter):
             threading.Thread(target=store.deliver, args=(report_id,), daemon=True).start()
 
         def log_message(self, format, *args):
-            print(f"{self.client_address_seen()} {format % args}", file=sys.stderr, flush=True)
+            # Without the client's address: it's only kept, in memory, for the rate limit
+            print(format % args, file=sys.stderr, flush=True)
 
     return Handler