fix #1924: use storage.session in mv2-bg

Author: tophf

src/js/storage-util.js

@@ -8,7 +8,5 @@ const StorageExtras = {
 
 export const chromeLocal =
   /*@__PURE__*/Object.assign(browser.storage.local, StorageExtras);
-/** @type {typeof import('chrome-types').chrome.storage.session} */
-export const chromeSession = __.MV3 &&
-  /*@__PURE__*/Object.assign(chrome.storage.session, StorageExtras);
+export const chromeSession = chrome.storage.session;
 export const GET_KEYS = !!chromeLocal.getKeys;