fix: unified Share Action types (#38351)

Summary:
This pull request simplifies the type and fixes a TypeScript object destructuring problem by combining the ShareSharedAction and ShareDismissedAction types into a single ShareAction type. Enabling proper access to the activityType property without TypeScript errors.

## Changelog:
[INTERNAL] [FIXED] -  Unified ShareSharedAction and ShareDismissedAction into ShareAction. Resolved TypeScript issue with object destructuring.

Pull Request resolved: https://github.com/facebook/react-native/pull/38351

Test Plan:
With the current typing:
![image](https://github.com/facebook/react-native/assets/7197169/40b43c40-ed6c-4b1a-8f43-0bb853920e20)

With the proposed solution:
![image](https://github.com/facebook/react-native/assets/7197169/af9e601b-780c-4c69-9a8c-11771a125a0c)

Reviewed By: NickGerleman

Differential Revision: D47527426

Pulled By: philIip

fbshipit-source-id: 9830cd993596bbac2dc07d9f37ca20b35f582156

packages/react-native/Libraries/Share/Share.d.ts

@@ -27,17 +27,11 @@ export type ShareOptions = {
   anchor?: number | undefined;
 };
 
-export type ShareSharedAction = {
-  action: 'sharedAction';
-  activityType?: string | undefined;
+export type ShareAction = {
+  action: 'sharedAction' | 'dismissedAction';
+  activityType?: string | null | undefined;
 };
 
-export type ShareDismissedAction = {
-  action: 'dismissedAction';
-};
-
-export type ShareAction = ShareSharedAction | ShareDismissedAction;
-
 export interface ShareStatic {
   /**
    * Open a dialog to share text content.

packages/react-native/types/__typetests__/index.tsx

@@ -84,8 +84,7 @@ import {
   SectionListProps,
   SectionListRenderItemInfo,
   Share,
-  ShareDismissedAction,
-  ShareSharedAction,
+  ShareAction,
   StatusBar,
   StyleProp,
   StyleSheet,