Hi,
We add that parameter so that just after an update, you and your customers don't get weird crashes of the interface because the javascript file is still cached by the browser while the view has been updated and the javascript and the view don't match anymore.
Note that browsers do cache resource files with parameters in the URL. So you won't gain anything in speed if you remove that parameter.
If you use a CDN like cloudflare, they might not cache the resources if there are parameters in the URL, as it is mentioned by GTMetrix. However, if you don't use a CDN for your website, then doing that change will help almost no one as not many people have proxy caching servers (maybe for some big companies).
All that would do is avoid people from the same company to request the resources of the page if someone else there already requested them no too long ago and only for the first page that they look at (since after the first page, their browser will cache the resource file). And that's only if the proxy cache server doesn't support caching with parameters in the URLs, which I suppose most do.
The benefit is so slim I would recommend not bothering as 99.9999% of the pages won't be impacted.
Now, if you really want to do it, you can remove the code:
?v='.HIKASHOP_RESSOURCE_VERSION
in the file administrator/components/com_hikashop/helpers/helper.php
Note however that you will loose the change after each update of HikaShop.
Alternatively, some optimization extension like JCHOptimize can prevent that as they combine the js/css files together in one cache file. You just have to clear their cache after each update of an extension/joomla/etc.