Avoid running PostGIS specific backends in all backends (#3036)
Avoid running PostGIS specific backends in all backends (#3036)


ibis-project/ibis,ibis-project/ibis,cpcloud/ibis,ibis-project/ibis,cpcloud/ibis,ibis-project/ibis,cloudera/ibis,cloudera/ibis,cpcloud/ibis,cpcloud/ibis,cloudera/ibis