fix test files

src/components/MainList.test.tsx

@@ -1,15 +1,16 @@
 import React from 'react';
+import { Browser } from 'webextension-polyfill';
 import { renderWithProviders } from '../utils/test-utils';
 import MainList from './MainList';
 
 jest.mock<typeof import('webextension-polyfill')>('webextension-polyfill', () => {
   return {
     runtime: {
-      getManifest: () => {
-        return { version: 'test-version' };
-      },
+      getManifest: () => ({
+        version: 'test-version',
+      }),
     },
-  };
+  } as Browser;
 });
 
 describe('MainList', () => {