[keyserver] Update tID in register response validator

Summary:
Fixes [ENG-4411](https://linear.app/comm/issue/ENG-4411)

`threadInfos` is a dict from threadID to threadInfo, so the domain should be marked as `tID`.

Test Plan: Try registering and confirm that there is no error. Try logging into the newly created account.

Reviewers: kamil, inka

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8546

keyserver/src/responders/user-responders.js

@@ -292,7 +292,7 @@ export const registerResponseValidator: TInterface<RegisterResponse> =
       loggedInUserInfoValidator,
     ]),
     cookieChange: tShape({
-      threadInfos: t.dict(t.String, rawThreadInfoValidator),
+      threadInfos: t.dict(tID, rawThreadInfoValidator),
       userInfos: t.list(userInfoValidator),
     }),
   });