Give performance bar cookie an expiry date

Without an expiry, it's a session cookie, which means it could be
cleared on browser exit.

app/assets/javascripts/behaviors/shortcuts/shortcuts.js

@@ -117,9 +117,9 @@ export default class Shortcuts {
     e.preventDefault();
     const performanceBarCookieName = 'perf_bar_enabled';
     if (parseBoolean(Cookies.get(performanceBarCookieName))) {
-      Cookies.set(performanceBarCookieName, 'false', { path: '/' });
+      Cookies.set(performanceBarCookieName, 'false', { expires: 365, path: '/' });
     } else {
-      Cookies.set(performanceBarCookieName, 'true', { path: '/' });
+      Cookies.set(performanceBarCookieName, 'true', { expires: 365, path: '/' });
     }
     refreshCurrentPage();
   }

changelogs/unreleased/set-performance-bar-cookie-expiry.yml

+---
+title: Set performance cookie to last for a year
+merge_request: 43692
+author:
+type: changed