message: Avoid duplication of `useful-not-found-page` on back button
diff: @@ -197,8 +197,7 @@ void features.add(import.meta.url, {
  pageDetect.is404,
  () => parseCurrentURL().length > 1,
  ],
  - deduplicate: 'has-rgh',
  - init: showMissingPart,
  + init: onetime(showMissingPart),
  },
  {
  asLongAs: [
  @@ -215,6 +214,5 @@ void features.add(import.meta.url, {
  pageDetect.isPRCommit404,
  ],
  awaitDomReady: false,
  - deduplicate: 'has-rgh',
  init: onetime(initPRCommit),
  });
  