Just set your category's leading items grid to have 3 columns and as many items you want (probably a multiplier of 3 to have an even grid). Then set 0 to the count for primary, secondary etc. (so you only show a single grid layout).

With K2, layouts like these are very simple to have, without any coding of course.

You can either locate the element using your browser's inspect tools and add a CSS rule to hide it (with display:none) or -better- follow this guide getk2.org/documentation/tutorials/templating-with-k2-and-the-concepts-of-sub-templates to create your own set of template overrides for K2 within your Joomla template.

Then you can edit your HTML (e.g. in category.php for your case) and remove any HTML you don't want.

Unlike default Joomla articles, K2 uses fewer override files. And you can also have different sets of overrides per category or categories.

Beyond that, explore category parameter inheritance (so you don't set the same category parameters over and over) and you'll see why K2 is the best option for content management in Joomla.