sweet: disable gVisor by default

gVisor is broken as of https://go.dev/cl/652276.

For golang/go#72042.
Fixes golang/go#68437.

Change-Id: I6a6a636caa3a65c3c58d30ed26d877dba9378afe
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/653755
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>