Improve modals reducer types (#26610)

app/javascript/mastodon/actions/modal.ts

@@ -1,12 +1,14 @@
 import { createAction } from '@reduxjs/toolkit';
 
+import type { ModalProps } from 'mastodon/reducers/modal';
+
 import type { MODAL_COMPONENTS } from '../features/ui/components/modal_root';
 
 export type ModalType = keyof typeof MODAL_COMPONENTS;
 
 interface OpenModalPayload {
   modalType: ModalType;
-  modalProps: unknown;
+  modalProps: ModalProps;
 }
 export const openModal = createAction<OpenModalPayload>('MODAL_OPEN');