Fix missing ParticipantSetInfo.id

[Frederick888]

Description

Fix missing ParticipantSetInfo.id. Property description copied from https://secure.echosign.com/public/docs/restapi/v6.

Not sure if this is the correct way to fix this? Should I fix it somewhere else and re-generate these files?

Motivation and Context

Discrepancy between Adobe Sign v6 specs, and the function we're currently working on needs this id to make potentially fewer API calls.

How Has This Been Tested?

Types of changes

• 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 signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes. (AgreementsApiTest doesn't validate response at the moment.)
• All new and existing tests passed.

Needs sign-off from @akarunamuni.

[gvageriya]

Approved as @akarunamuni is on leave

[Frederick888]

CLA signed. Thanks, Gaurav!

[Frederick888]

DetailedParticipantInfo.userId is also missing.