Model names in documentation

[gaborvar]

https://github.com/Azure-Samples/azure-search-openai-demo/blob/dee23757a4b8ba264b7f7161ace103d4d2b18dbc/docs/deploy_existing.md?plain=1#L30C145-L30C146 refers to 'gpt-4o-turbo' as default in line30.
In https://github.com/Azure-Samples/azure-search-openai-demo/blob/dee23757a4b8ba264b7f7161ace103d4d2b18dbc/docs/deploy_features.md 'gpt-4o-mini' is stated as default.

Step 6 (line 31) states that default version is 0125.

[pamelafox]

Thank you! Fixing in #2499