[Datafactory] Updated UserProperties model in Activities

[hvermis]

Description

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[shahabhijeet]

This is a breaking change and should be reflected in the version.
You have a download base of ~1600 as of now for V1.0.0.
With this change you are essentially breaking all of them.
Remove addtionalProperties could have been discussed if it falls under breaking change as it's still a optional parameter, but changing data type of userProperties is for user a breaking change and should be treated according.
Also PackageRelease notes should reflect accordingly.
The code change seems fine.
You need to update version to 2.0.0 and mention the breaking change in the package release notes.

[shahabhijeet]

@hvermis can you add the link to the spec PR that was merged for this change.

[hvermis]

We didn't mean to remove additionaProperties, bringing them back.
The user properties is a new feature not used by customers yet, but we will add them as breaking change.

[hvermis]

Azure spec PR-s
Azure/azure-rest-api-specs#3483
Azure/azure-rest-api-specs#3493

[hvermis]

@shahabhijeet The spec PR-s are merged, and I updated according to your comments