fix: reduce granian backpressure

This limits amount of possible database connections.

Author: nijel

etc/supervisor/conf.d/web.conf

@@ -5,6 +5,7 @@ command = /app/venv/bin/granian
     --runtime-mode st
     --interface wsgi
     --runtime-threads 4
+    --backpressure 16
     --workers %(ENV_WEB_WORKERS)s
     --uds /run/granian/weblate.socket
     weblate.wsgi:application