There is no such feature. A quick way to do it would be to hide the reactions selector with CSS, such as:
.category-general-resources .discourse-reactions-picker {
display: none;
}
If you want to iterate through multiple categories and make it easier to maintain, you can use a SCSS loop like this:
$categories: 'general', 'site-feedback', 'staff';
@each $category in $categories {
.category-#{$category} .discourse-reactions-picker {
display: none;
}
}
The category class is visible in the <body>
tag.
It can be circumvented by any user that knows how to make it visible again client-side, but if your community is well-behaved, I think it’s a good workaround.