model environment variable should be case insensitive

[pylanglois]

crewai create ... with Azure options generates a .env file with a lowercase model, but the code tries to load an uppercase MODEL, which falls back to the default model.

Here is the line that breaks the execution:

crewAI/src/crewai/utilities/llm_utils.py

Line 80 in 1b488b6

or os.environ.get("MODEL")

The resulting trace looks like this:

Error during LLM call: litellm.AuthenticationError: AuthenticationError: OpenAIException - The api_key client option must be set either by passing api_key to the client or by setting the OPENAI_API_KEY environment variable
python-BaseException