Refactor PrivacyDropdown to TypeScript (#36979)

app/javascript/mastodon/features/ui/components/boost_modal.tsx

@@ -52,7 +52,10 @@ export const BoostModal: React.FC<{
   }, [onClose]);
 
   const findContainer = useCallback(
-    () => document.getElementsByClassName('modal-root__container')[0],
+    () =>
+      document.getElementsByClassName(
+        'modal-root__container',
+      )[0] as HTMLDivElement,
     [],
   );