You can hide things in Microthemer using CSS styling, but not remove them.
Select the element you want to hide. In this case, you would probably select the paragraph that hold the Event settings text as well as the select field.
Go to the Behaviour property group and set the display property to none.
If the default option in the select menu is “Yes”, then that’s problem solved. But if it’s “No”, you will need to find a way to modify the HTML on the page. This can be done with JavaScript, if it can’t be done via the WooCommerce settings.
Here is some code that will work as long as the select menu gets loaded when the page first renders, instead of being added after a delay:
(Go to Settings > View > Full code editor and past it on the JavaScript tab)