KMS keys for a dataset should be allowed for getting updated

**Is your idea related to a problem? Please describe.**
I have a dataset which I imported with a KMS key - A but now I have a new KMS key - B. I wanted to update the KMS key of my dataset. 

**Describe the solution you'd like**
Data.all should allow updating the KMS key of the dataset

*P.S. Don't attach files. Please, prefer add code snippets directly in the message body.*
