Fix mute duration not being shown in list of muted accounts in web UI (#32388)

app/javascript/mastodon/models/account.ts

@@ -95,6 +95,9 @@ export const accountDefaultValues: AccountShape = {
   limited: false,
   moved: null,
   hide_collections: false,
+  // This comes from `ApiMutedAccountJSON`, but we should eventually
+  // store that in a different object.
+  mute_expires_at: null,
 };
 
 const AccountFactory = ImmutableRecord<AccountShape>(accountDefaultValues);