There isn’t an option in the user’s preferences to remove the Latest threads from the Categories page.
I believe this is a setting which only the moderator(s)/administrator(s) of the Discourse Forum platform can configure.
A workaround I can think of, is a CSS hack for the Categories page in your browser, in order to display only the sections you want and remove anything else.
Firefox allows CSS hacks for specific pages, I’m not sure if this is possible in other browsers.
In any case, there is an addon called Stylus, which can overwrite CSS rules for web pages and can be installed in most browsers.
Let me know if you’re interested in that approach - and which browser you’re using - so I can have a look at it.