fix gemma4 to vllm weight conversion

[aireenmei]

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/utils/model_creation_utils.py	50.00%	1 Missing ⚠️

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