Move data_processing_test to cpu

[aireenmei]

Description

data_processing tests are the top time consuming tests on TPU runner. But it data loading only requires CPU. This PR moves the tests to cpu_only to save TPU runner resources.

Tests

NA

Checklist

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[A9isha]

thanks Aireen!