fix: fix the type of NavigationJumpToActionPayload (#6210)

As mentioned in https://reactnavigation.org/docs/en/switch-actions.html
the param which's name is 'key' of `SwitchActions.jumpTo()`  should be optional

typescript/react-navigation.d.ts

@@ -345,7 +345,7 @@ declare module 'react-navigation' {
 
   export interface NavigationJumpToActionPayload {
     routeName: string;
-    key: string;
+    key?: string;
     params?: NavigationParams;
   }