Non-standard VERTCRS.DATUM constructs

csv/pe_list_vertcs.csv contains WKT2 strings like:
```VERTCRS["WGS_1984_(G2139)_height",DATUM["WGS_1984_(G2139)",ELLIPSOID["WGS_1984",6378137.0,298.257223563,LENGTHUNIT["Meter",1.0]]],CS[vertical,1],AXIS["Ellipsoidal height (h)",up,LENGTHUNIT["Meter",1.0]]]```

The presence of a DATUM[] doesn't conform with the grammar at http://docs.opengeospatial.org/is/18-010r7/18-010r7.html#84.

More fundamentally ellipsoidal heights Vertical CRS aren't valid in ISO 19111:2019. Cf "Note 2: Ellipsoidal heights cannot be captured in a vertical coordinate reference system. They exist only as an inseparable part of a 3D coordinate tuple defined in a geographic 3D coordinate reference system." in table 12 of https://docs.opengeospatial.org/as/18-005r4/18-005r4.html