I find it strange that this happens with Yoast as it points the canonical tag for the homepage to a 301 redirect URL. I don't think it's a big problem as search engines seem to handle it well, but it's a problem that I wouldn't expect to see in such a popular and reputable SEO plugin.
If you use the plugin editor to remove the trailing slash you will remove the trailing slash from all pages of your site (something you may not want to do).
If you only want to remove the trailing slash from the homepage the easiest option would be to manually add the canonical URL without the trailing slash in the Advanced tab for Yoast when editing the homepage (as Linda said above). Doing this for one page will take you 2 seconds and fix the problem!