fix: Silence model not found log (#1470)

<!-- .github/pull_request_template.md -->

## Description
<!--
Please provide a clear, human-generated description of the changes in
this PR.
DO NOT use AI-generated descriptions. We want to understand your thought
process and reasoning.
-->
Basically, when the LLM Model is not specified, we put
`openai/gpt-4o-mini` as the model name. In litellm's `model_cost` map,
there is no such entry. There is however `gpt-4o-mini`, so when that is
specified for example, this log doesn't appear.

My solution was to just move this from info log to debug log, if it is
not a critical error. We could also change the default name, if it
doesn't break anything else.

## Type of Change
<!-- Please check the relevant option -->
- [ ] Bug fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
- [ ] Code refactoring
- [ ] Performance improvement
- [ ] Other (please specify):

## Screenshots/Videos (if applicable)
<!-- Add screenshots or videos to help explain your changes -->

## Pre-submission Checklist
<!-- Please check all boxes that apply before submitting your PR -->
- [ ] **I have tested my changes thoroughly before submitting this PR**
- [ ] **This PR contains minimal changes necessary to address the
issue/feature**
- [ ] My code follows the project's coding standards and style
guidelines
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have added necessary documentation (if applicable)
- [ ] All new and existing tests pass
- [ ] I have searched existing PRs to ensure this change hasn't been
submitted already
- [ ] I have linked any relevant issues in the description
- [ ] My commits have clear and descriptive messages

## DCO Affirmation
I affirm that all code in every commit of this pull request conforms to
the terms of the Topoteretes Developer Certificate of Origin.

cognee/infrastructure/llm/utils.py

@@ -62,7 +62,7 @@ def get_model_max_completion_tokens(model_name: str):
         max_completion_tokens = litellm.model_cost[model_name]["max_tokens"]
         logger.debug(f"Max input tokens for {model_name}: {max_completion_tokens}")
     else:
-        logger.info("Model not found in LiteLLM's model_cost.")
+        logger.debug("Model not found in LiteLLM's model_cost.")
 
     return max_completion_tokens