[Config] Add hint to disable Solr if you do not want a readable index in solr-vol-1

update.sh

@@ -232,6 +232,7 @@ for option in ${CONFIG_ARRAY[@]}; do
     if ! grep -q ${option} mailcow.conf; then
       echo "Adding new option \"${option}\" to mailcow.conf"
       echo '# Solr is disabled by default after upgrading from non-Solr to Solr-enabled mailcows.' >> mailcow.conf
+      echo '# Disable Solr or if you do not want to store a readable index of your mails in solr-vol-1.' >> mailcow.conf
       echo "SKIP_SOLR=y" >> mailcow.conf
   fi
   elif ! grep -q ${option} mailcow.conf; then