WebUI: provide semantic information of table body

From https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tbody#usage_notes :
>Specifying such table content groups also provides valuable contextual
>information for assistive technologies

src/webui/www/.htmlvalidate.json

@@ -8,7 +8,6 @@
     "no-conditional-comment": "off",
     "no-inline-style": "off",
     "prefer-button": "off",
-    "prefer-tbody": "off",
     "text-content": "off",
     "void-style": "off",
     "wcag/h63": "off",