add troubleshooting hint
add troubleshooting hint

- Loading file-diff-list is slow

eekboom/gerrit-intellij-plugin,uwolfer/gerrit-intellij-plugin,vogellacompany/gerrit-rest-java-client,sstafford/gerrit-rest-java-client,uwolfer/gerrit-rest-java-client,vogellacompany/gerrit-rest-java-client,uwolfer/gerrit-rest-java-client,sstafford/gerrit-rest-java-client