Remove Interval Start and Interval End from ERCOT SCED 60 Day Datasets

[WillKoehrsen]

Summary

• Removes "Interval Start" and "Interval End" from ERCOT SCED Gen and Load Resource 60 day
• We are removing these columns because these are SCED datasets and we can rely on the SCED Timestamp column

Validation

• Run tests with VCR_RECORD_MODE=all uv run pytest gridstatus/tests/source_specific/test_ercot_api.py -k 60_day_sced_disclosure

[WillKoehrsen]

Merging this without approval because we told customers we'd update these datasets at 9 am CST and our downstream code needs this update.