Looking at the html of the page:
It looks like you may need to hide the class ‘header_buy_row’. It’s worth checking around if this appears in a different part of the page that you want to be visible. After a quick search I couldn’t find any other instance.
There are multiple ways to hide it, each with their cons and pros. Once I could think is with CSS:
display: none;
That removes it from the page so that it doesn’t consume any space, but it might move some other elements around.
I hope this helps, I haven’t tried custom CSS on Itch, so I’m not aware of any pitfalls this might create.