use span as default element for Hidden component

This improves the HTML DOM tree if this happens to be used in let's say
a `p` tag where `div` elements are not allowed. The `Hidden` element is
hidden so it doesn't really matter what the underlying element is.

Fixes: #3319

packages/@headlessui-react/src/components/tabs/tabs.tsx

@@ -649,7 +649,7 @@ function PanelFn<TTag extends ElementType = typeof DEFAULT_PANEL_TAG>(
   )
 
   if (!selected && (theirProps.unmount ?? true) && !(theirProps.static ?? false)) {
-    return <Hidden as="span" aria-hidden="true" {...ourProps} />
+    return <Hidden aria-hidden="true" {...ourProps} />
   }
 
   return render({

packages/@headlessui-react/src/internal/hidden.tsx

@@ -2,7 +2,7 @@ import type { ElementType, Ref } from 'react'
 import type { Props } from '../types'
 import { forwardRefWithAs, render, type HasDisplayName, type RefProp } from '../utils/render'
 
-let DEFAULT_VISUALLY_HIDDEN_TAG = 'div' as const
+let DEFAULT_VISUALLY_HIDDEN_TAG = 'span' as const
 
 export enum HiddenFeatures {
   // The default, no features.