Bug fixes

• Fixed the sponsors_listing column in github_my_organization, github_organization, github_organization_member, github_team_member, and github_user tables to no longer error when the sponsors listing has a next payout date. The next_payout_date field is now returned as a date (e.g., 2024-08-11), or null when unset. (#563) (Thanks @dark-panda for the contribution!)