chore(i18n): remove orphaned dashboard keys from en.json

The Dashboard settings component was deleted earlier in this branch
(8eeb571f), leaving home.settings.dashboard.title and
home.settings.dashboard.sessions_title referenced nowhere.
Removed via i18n:check --fix-unused; sv.json never had them.

translations/en.json

@@ -431,10 +431,6 @@
           "4_hours": "4 hours",
           "24_hours": "24 hours"
         }
-      },
-      "dashboard": {
-        "title": "Dashboard",
-        "sessions_title": "Sessions"
       }
     },
     "sessions": {