"stale GRV proxy detected" code probe is not hit in a Joshua ensemble

[sfc-gh-tclinkenbeard]

This code probe, from DatabaseContext::isCurrentGrvProxy, is currently not hit in a 250k-test Joshua ensemble.

[jzhou77]

This probe can only be hit when ENABLE_VERSION_VECTOR and ENABLE_VERSION_VECTOR_TLOG_UNICAST are enabled. I'll try if we can hit with these knobs on.