Don't specify lastRefreshTime in integration tests

Since specifying this when importing users isn't supported.

Author: rsgowman

test/integration/auth.spec.ts

@@ -2517,7 +2517,8 @@ describe('admin.auth', () => {
         metadata: {
           lastSignInTime: now,
           creationTime: now,
-          lastRefreshTime: null,  // TODO(rsgowman): Switch to 'now' once importing users supports lastRefreshTime
+          // TODO(rsgowman): Enable once importing users supports lastRefreshTime
+          //lastRefreshTime: now,
         },
         providerData: [
           {