test: align stale tests with merged Codex preset and bucket changes

CI on main was red because two tests did not follow intentional changes
that were already merged into the codebase:

- codexChatProviderPresets.test.ts still expected the "Kimi For Coding"
  preset, which was removed in 16c3ef3f. Drop the corresponding entry
  from the expected presets map.
- import_export_sync.rs still asserted the legacy per-provider
  model_provider id ("rightcode"), but 9fac15b8 unified Codex
  third-party providers into the stable "custom" history bucket. Mirror
  the assertion update already applied to provider_service.rs.

No production code changed; both fixes only update test expectations.