Update popover declaration for compatibility with Preact typings

Preact's latest typings allow setting popover to a boolean value, but this still
renders `popover="true"` and "true" is an invalid value. Instead set the value
to "auto" which is the default value [1].

[1] https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/popover

Author: robertknight

src/components/input/SelectNext.tsx

@@ -287,7 +287,7 @@ function SelectMain<T>({
   const buttonRef = useSyncedRef(elementRef);
   const defaultButtonId = useId();
   const extraProps = useMemo(
-    () => (listboxAsPopover ? { popover: '' } : {}),
+    () => (listboxAsPopover ? { popover: 'auto' } : {}),
     [listboxAsPopover],
   );