Refactor: Remove duplicate _has_json_arrow_type from loader.py

[shuoweil]

This PR eliminates a redundant function, _has_json_arrow_type, from bigframes/session/loader.py. The logic of this function is identical to bigframes.dtypes.contains_db_dtypes_json_arrow_type.

The call to the removed function within _validate_dtype_can_load has been updated to utilize the existing bigframes.dtypes.contains_db_dtypes_json_arrow_type.

This refactoring improves code maintainability and reduces duplication by centralizing the logic for checking JSON arrow types.

[tswast]

Thanks!

[tswast]

Presubmit failures:

FAILED tests/system/small/blob/test_io.py::test_blob_create_from_uri_str - As...
FAILED tests/system/small/blob/test_io.py::test_blob_create_from_glob_path - ...
FAILED tests/system/small/blob/test_io.py::test_display_images - AssertionErr...
FAILED tests/system/small/blob/test_properties.py::test_blob_authorizer - Ass...
FAILED tests/system/small/blob/test_properties.py::test_blob_version - Assert...
FAILED tests/system/small/blob/test_properties.py::test_blob_metadata - Asser...
FAILED tests/system/small/blob/test_properties.py::test_blob_content_type - T...
FAILED tests/system/small/blob/test_properties.py::test_blob_md5_hash - TypeE...
FAILED tests/system/small/ml/test_multimodal_llm.py::test_multimodal_embedding_generator_predict_default_params_success
FAILED tests/system/small/blob/test_properties.py::test_blob_size - Assertion...
FAILED tests/system/small/blob/test_properties.py::test_blob_updated - Assert...
FAILED tests/system/small/bigquery/test_ai.py::test_ai_if_multi_model - asser...
FAILED tests/system/small/bigquery/test_ai.py::test_ai_classify_multi_model

These are all blob or ai related. I'll see if this is a recurring issue and file an issue to make these more robust.

[shuoweil]

Presubmit failures:

FAILED tests/system/small/blob/test_io.py::test_blob_create_from_uri_str - As...
FAILED tests/system/small/blob/test_io.py::test_blob_create_from_glob_path - ...
FAILED tests/system/small/blob/test_io.py::test_display_images - AssertionErr...
FAILED tests/system/small/blob/test_properties.py::test_blob_authorizer - Ass...
FAILED tests/system/small/blob/test_properties.py::test_blob_version - Assert...
FAILED tests/system/small/blob/test_properties.py::test_blob_metadata - Asser...
FAILED tests/system/small/blob/test_properties.py::test_blob_content_type - T...
FAILED tests/system/small/blob/test_properties.py::test_blob_md5_hash - TypeE...
FAILED tests/system/small/ml/test_multimodal_llm.py::test_multimodal_embedding_generator_predict_default_params_success
FAILED tests/system/small/blob/test_properties.py::test_blob_size - Assertion...
FAILED tests/system/small/blob/test_properties.py::test_blob_updated - Assert...
FAILED tests/system/small/bigquery/test_ai.py::test_ai_if_multi_model - asser...
FAILED tests/system/small/bigquery/test_ai.py::test_ai_classify_multi_model

These are all blob or ai related. I'll see if this is a recurring issue and file an issue to make these more robust.

Thanks Tim. I have a feeling it is the bigquery change brings in this failure. I am the oncall this week. I am investigating for the it now.