Conditionally branch tokamax.ragged_dot calls based on use_manual_quantization

[zxhe-sean]

Description

Conditionally branch tokamax.ragged_dot calls based on use_manual_quantization to avoid passing None to manual_axis_type

The ubench nightly tests broke due to TypeError: ragged_dot() got an unexpected keyword argument 'manual_axis_type'

FIXES: b/511266446

Tests

Tested locally with AOT compiling and successfully compiled.

Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/kernels/megablox/ops.py	0.00%	9 Missing ⚠️

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