[web] Trivial fix for non-static interop JS interop class. (#38126)

lib/web_ui/lib/src/engine/js_interop/js_promise.dart

diff --git a/lib/web_ui/lib/src/engine/js_interop/js_promise.dart b/lib/web_ui/lib/src/engine/js_interop/js_promise.dart
index 1332715..45f3f3b 100644
--- a/lib/web_ui/lib/src/engine/js_interop/js_promise.dart
+++ b/lib/web_ui/lib/src/engine/js_interop/js_promise.dart
@@ -9,6 +9,7 @@
 
 /// Type-safe JS Promises
 @JS('Promise')
+@staticInterop
 abstract class Promise<T> {
   /// A constructor for a JS promise
   external factory Promise(PromiseExecutor<T> executor);