Auto Update is enabled by default, you can disable it under Settings → Updates → Automatic Updates on/off
You will also be informed after the installation of hestia is finished: https://github.com/hestiacp/hestiacp/blob/8e399f2ab2227dd31d38cebebb738b163534c8d5/install/hst-install-ubuntu.sh#L1930-L1931
Please follow the best practice and do not edit the default templates, please copy them as you can find in our docs: Getting Started | Hestia Control Panel
Just as last word: If you follow the template best practice, there would not be need to disable autoupdate.