update upgrade documentation

onlyoffice-docker-upgrade.rst

@@ -47,3 +47,8 @@ If using documentserver standalone (integration edition)::
   docker rename documentserver documentserver-$(date +%s)
   docker run -i -t -d -p 80:80 -p 443:443 --name documentserver -v /app/onlyoffice/DocumentServer/data:/var/www/onlyoffice/Data -e POSTGRESQL_SERVER_HOST=localhost -e JWT_ENABLED=true -e JWT_SECRET=s3cr3t --restart=always onlyoffice/documentserver-ie
 
+
+Also:
+ - set the sessionidle parameter for the document server
+ - open the browser and check that the docuument server settings for maintaining revisions are set 
+