OpenAI: Migrating to HTTPX2

OpenAI's Python SDK has migrated to HTTPX2 for its HTTP clients, which is now installed automatically and no longer requires the separate httpx package. The migration maintains backward compatibility for default use cases, but introduces a key change where HTTPX2 uses the operating system's trust store instead of certifi's CA bundle, which may require configuration adjustments in containerized or corporate proxy environments. Developers can manage certificate verification by setting SSL environment variables or explicitly configuring an SSLContext when using custom HTTP clients.