Revert "[cobalt] Enable encryption to the shuffler."

This reverts commit 81345fa6.

Reason for revert: There is evidence decryption is failing in the backend.

Original change's description:
> [cobalt] Enable encryption to the shuffler.
> 
> testing=manual
> 
> Change-Id: I1f68574278249f879fce7b2bb8fb6325f6f75b8a

TBR=azani@google.com,pesk@google.com

Change-Id: I3d12510f82065f8999c8c0a68eb87b26a881a94c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true