32ef1588e8
GPT-5.5 was correctly removed from codex-free tier in 7b89583c
(since free accounts cannot access it), but the test was not updated
to reflect this. This caused TestCodexStaticModelsIncludeGPT55 to
fail on the free subtest.
Changes:
- Remove free tier from GPT-5.5 inclusion test
- Add new TestCodexFreeModelsExcludeGPT55 to explicitly verify
that free tier does NOT include GPT-5.5