Slot: Fix React Element type check for lazy components

Co-authored-by: Jenna Smith <jjenzz@users.noreply.github.com>

The `React.isValidElement(element)` check in `isLazyComponent` returned `false`
for lazy elements in a NextJS prod build (unclear yet if this is just a Next
thing or an issue with the prod build of React). Changing the check to
`'$$typeof' in element` fixes it.

Author: chaance

packages/react/slot/src/slot.tsx

@@ -31,7 +31,9 @@ function isPromiseLike(value: unknown): value is PromiseLike<unknown> {
 
 function isLazyComponent(element: React.ReactNode): element is LazyReactElement {
   return (
-    React.isValidElement(element) &&
+    element != null &&
+    typeof element === 'object' &&
+    '$$typeof' in element &&
     element.$$typeof === REACT_LAZY_TYPE &&
     '_payload' in element &&
     isPromiseLike(element._payload)