docs: fix return type of setJumpList() in electron.d.ts (#33964)

Before:
```ts
setJumpList(categories: (JumpListCategory[]) | (null)): void;
```

After:
```ts
setJumpList(categories: (JumpListCategory[]) | (null)): ('ok' | 'error' | 'invalidSeparatorError' | 'fileTypeRegistrationError' | 'customCategoryAccessDeniedError');
```

Fixes: https://github.com/electron/electron/issues/33909
Signed-off-by: Darshan Sen <raisinten@gmail.com>

Co-authored-by: Darshan Sen <raisinten@gmail.com>

docs/api/app.md

@@ -861,6 +861,8 @@ Returns `Object`:
 
 * `categories` [JumpListCategory[]](structures/jump-list-category.md) | `null` - Array of `JumpListCategory` objects.
 
+Returns `string`
+
 Sets or removes a custom Jump List for the application, and returns one of the
 following strings: