Removes eager creation of Outcome from SANO (#10153)

## What changed?
Removes eager creation of the outcome for standalone nexus operations.

## Why?
The eager creation leaves an Outcome around without a variant. This
means if the SANO fails, in some circumstances, we'll look up the empty
outcome for our result. This does correctly return LastAttemptFailure,
but it also trips a softassert.

## How did you test it?
- [x] built
- [ ] run locally and tested manually
- [x] covered by existing tests
- [ ] added new unit test(s)
- [ ] added new functional test(s)

Author: S15

chasm/lib/nexusoperation/operation.go

@@ -127,7 +127,6 @@ func newStandaloneOperation(
 		UserMetadata: frontendReq.GetUserMetadata(),
 		Identity:     frontendReq.GetIdentity(),
 	})
-	op.Outcome = chasm.NewDataField(ctx, &nexusoperationpb.OperationOutcome{})
 	op.Visibility = chasm.NewComponentField(ctx, chasm.NewVisibilityWithData(
 		ctx,
 		frontendReq.GetSearchAttributes().GetIndexedFields(),