docs: Fixed a small syntax issue in the ModelClass Update fine-tuning.md

[mdqst]

I noticed a syntax issue in the ModelClass enum where a comma was missing after the EMBEDDING value. This would have caused a compilation error or unexpected behavior. I've added the necessary comma so the code functions as intended.

Here’s the fix I applied:

Before:

enum ModelClass {
    SMALL,    // Fast, efficient for simple tasks
    MEDIUM,   // Balanced performance and capability
    LARGE,    // Most capable but slower/more expensive
    EMBEDDING // Specialized for vector embeddings
    IMAGE     // Image generation capabilities
}

After:

enum ModelClass {
    SMALL,    // Fast, efficient for simple tasks
    MEDIUM,   // Balanced performance and capability
    LARGE,    // Most capable but slower/more expensive
    EMBEDDING, // Specialized for vector embeddings
    IMAGE     // Image generation capabilities
}

This minor adjustment ensures that the values are properly separated in the enum, preventing potential issues down the line.