fix(i18n): correct the spelling of Favorite in the US (#2807)

locales/en.json

@@ -661,7 +661,7 @@
       "sign_up": "Sign-Up"
     },
     "notifications_all": "All",
-    "notifications_favourite": "Favourite",
+    "notifications_favourite": "Favorite",
     "notifications_follow": "Follow",
     "notifications_follow_request": "Follow request",
     "notifications_mention": "Mentions",