postgresql: bump shm size and disable parallel queries

https://forum.cloudron.io/topic/5604/nextcloud-take-very-long-time-to-respond/5

src/services.js

@@ -1310,6 +1310,7 @@ async function startPostgresql(existingInfra) {
                 --log-opt tag=postgresql \
                 --dns 172.18.0.1 \
                 --dns-search=. \
+                --shm-size=128M \
                 -e CLOUDRON_POSTGRESQL_ROOT_PASSWORD="${rootPassword}" \
                 -e CLOUDRON_POSTGRESQL_TOKEN="${cloudronToken}" \
                 -v "${dataDir}/postgresql:/var/lib/postgresql" \