auth: remove flake from TestLockoutStore
Created by: keegancsmith
This test flaked on me just one too many times, so here is a fix :) The root cause is if expected expiryTime is generated within a different second of GenerateUnlockAccountURL we will get an unexpected ExpiresAt. This commit adjusts the test to instead allow any expiry time within 10s of our expectation.
Test Plan: go test