Fix Flow from #19239 (#19242)

packages/react-dom/src/events/isEventSupported.js

@@ -33,7 +33,7 @@ function isEventSupported(eventNameSuffix: string): boolean {
   if (!isSupported) {
     const element = document.createElement('div');
     element.setAttribute(eventName, 'return;');
-    isSupported = typeof element[eventName] === 'function';
+    isSupported = typeof (element: any)[eventName] === 'function';
   }
 
   return isSupported;

packages/react-dom/src/events/plugins/ModernSimpleEventPlugin.js

@@ -62,7 +62,7 @@ function extractEvents(
       // Firefox creates a keypress event for function keys too. This removes
       // the unwanted keypress events. Enter is however both printable and
       // non-printable. One would expect Tab to be as well (but it isn't).
-      if (getEventCharCode(nativeEvent) === 0) {
+      if (getEventCharCode(((nativeEvent: any): KeyboardEvent)) === 0) {
         return;
       }
     /* falls through */