feat: Set keepalive to 60 on gunicorn (#17897)

Set keepalive to 60 on gunicorn

The default is 2 seconds, the default for ALBs is 30 seconds

This can cause a race condition where gunicorn closes the connection
as the ALB sends a request, resulting in a 502.

bin/docker-server

@@ -20,6 +20,7 @@ exec gunicorn posthog.wsgi \
     --worker-tmp-dir /dev/shm \
     --workers=2 \
     --threads=8 \
+    --keep-alive=60 \
     --backlog=${GUNICORN_BACKLOG:-1000} \
     --worker-class=gthread \
     ${STATSD_HOST:+--statsd-host $STATSD_HOST:$STATSD_PORT} \