fix: Removing url from provider definition for good

[kysely]

Description

Motivation and Context

When mapping older “flat” provider API response, the url was assigned undefined value instead of actually removing it from the object. This PR fixes that.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTION_GUIDE document.
• [ ] I haven't repeated the code. (DRY)
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[janhalama]

@kysely thanks for fixing it