GDAL 2.2.4 has been released, and unlike previous releases the virtual
ABI dependency was not bumped, and so no transition is required this time.
The diff looked sane enough, and no symbols changes occurred, so I was
willing to try not requiring a transition for this GDAL release. I had
initially planned to try that starting with GDAL 2.3.0 to have a nice
round ABI dependency, but alas.