AIP-72: Updated test_file_task_handler_when_ti_value_is_invalid and test_file_task_handler

[henry3260]

• Updated test_file_task_handler_when_ti_value_is_invalid and test_file_task_handler to use structlog-based logging.
• Replaced ti.log with logging.getLogger(TASK_LOGGER) to access the logger.
• Directly tested FileTaskHandler by extracting it from logger handlers.
• Removed @pytest.mark.xfail as the tests now pass with the new logging system.
• Simplified assertions to match structlog's simpler log format.

closes: #50977

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