You can remove the chat widget from the Help Center, but keep it on other sites you have embedded in on by editing the Help Center Templates.
In Admin, go to Help Center > Help Center Design, scroll down to the Template Editor section, and select Open Template Editor
At the bottom of the template you'll see a section you will see the following line:
Simply remove this line of code and press Save. Make sure to press 'Save' in the main editor to ensure the widget is removed.
If you wanted to disable chat everywhere, you could disable it from Admin > Channels > Chat > Messenger Setup and then turn off the Messenger widget by clicking on the toggle.
That would disable chat on the Help Center and on any websites where you had embedded the Chat Widget. The advantage of the method explained in this article is that it removes chat from the Help Center only.