httpx http2 extra required for Gold Stack upgrades

When upgrading MCP server pyproject.toml to Gold Stack v18.1, httpx>=0.28.0 without [http2] extra installs successfully but crashes at runtime with “Using http2=True, but the ‘h2’ package is not installed”. The h2 package is only pulled in by the [http2] extra. Always use httpx[http2]>=0.28.0 when the API client enables HTTP/2 via http2=True in httpx.AsyncClient.