This will allow us to test protocol 2 in a stage environment before
removing the override to make 2 the default.
We may have seen a bug where something in celery (or an
associated library) was adding headers to a v1 message as
if it were a v2 message, which caused a bug in ddtrace; such
things may become more likely over time as code is written
with the assumption of v2 messages. Moving to v2 will avoid
those issues.
See https://github.com/edx/edx-arch-experiments/issues/800 for further details.
22b9ced6c0