Fix S3ToRedshiftOperator does not support default values on UPSERT

[dashton90]

This commit corrects a bug where upserts fail into tables with default, non-null columns

closes: #30341

[boring-cyborg]

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[cjames23]

@eladkal this looks good to me and was the approach I was going to take when I had planned on cutting a PR Friday.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.