IdentityManager c'tor now requires SigninClient.

Chromium change:

https://source.chromium.org/chromium/chromium/src/+/f4acc35c8036b10efe9180fae50e1ca1b71a3077

commit f4acc35c8036b10efe9180fae50e1ca1b71a3077
Author: Nohemi Fernandez <fernandex@chromium.org>
Date:   Fri Oct 13 12:32:33 2023 +0000

    Use SigninClient::IsClearPrimaryAccountAllowed to prevent signout for
    supervised users.

    Bug: 1324567

components/signin/public/identity_manager/brave_identity_manager_unittest.cc

@@ -156,6 +156,7 @@ class BraveIdentityManagerTest : public testing::Test {
     init_params.gaia_cookie_manager_service =
         std::move(gaia_cookie_manager_service);
     init_params.primary_account_manager = std::move(primary_account_manager);
+    init_params.signin_client = &signin_client_;
     init_params.token_service = std::move(token_service);
 
     identity_manager_ =