fix: remove --2a886c8_chip_config_name flag in sparsecore offloading

[RUEI4341]

Description

The flag is unsupported in libtpu versions greater than 0.0.24. Since our current environment uses v0.0.30+, the flag is obsolete.
Confirmed with rishabhbaghel@google.com that this flag is not in use across our stack.

FIXES: b/474511786

Tests

Training with the --2a886c8_chip_config_name flag
Training without the --2a886c8_chip_config_name flag

Checklist

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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