Like @dorukayhan said, the most likely explanation is that you visited a site which loaded something (maybe an image, a video) that McAfee considers a virus. It’s sitting in the cache directory since that’s the general mechanism by which the browser avoids re-downloading all of the page assets when you visit the same page later. It does however not have anything to do with Brave itself. It’s coming from from a website that was visited in the past.
Your best option here is to simply clear your cache. That will remove anything that will have been saved due to any previous website visits.
You can do that by going into:
Privacy and security
Clear browsing data
Selecting “All time” next to time range.
Selecting only “Cached images and files” from the checkboxes.