Microsoft Foundry Retires gpt-4.1 and Remaining gpt-4o Versions

gpt-4.1, gpt-4.1-mini, gpt-4.1-nano, gpt-4o (2024-08-06, 2024-11-20) and gpt-4o-mini retire from Azure OpenAI; gpt-5.1 is the named replacement for gpt-4o.