rename gpt-4o-mini and gpt-4.1-mini

[houtanb]

for consistency with other names, even though there's only one variant

gpt-4o-mini ➡️️ gpt-4o-mini-2024-07-18
gpt-4.1-mini ➡️️ gpt-4.1-mini-2025-04-14

https://platform.openai.com/docs/models/gpt-4o-mini
https://platform.openai.com/docs/models/gpt-4.1-mini