[gemma4] infer from config instead of hardcoding (#45606)
* infer from config instead of hardcoding
* Update test_modeling_gemma4.py
* Update modeling_gemma4.py
* Update modeling_gemma4.py
* Update modeling_gemma4.py
* make style
* add small docstring for reference
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Co-authored-by: omar zoloev <ozoloevwork@gmail.com>
Co-authored-by: vasqu <antonprogamer@gmail.com>
