PostGIS upgrade tests trying to downgrade

[robe]

I think there is something wrong with our postgres upgrade regress tests in that it's trying future versions to downgrade.

Debbie is failing on PostGIS 3.0 upgrade test with: ​https://debbie.postgis.net/job/PostGIS_Regress/13498/consoleFull

15:05:26 PostgreSQL 12.0 on x86_64-pc-linux-gnu, compiled by gcc (Debian 9.2.1-9) 9.2.1 20191008, 64-bit
15:05:26   Postgis 3.0.1dev - r17988 - 2019-11-06 20:01:22
15:05:26   scripts 3.0.1dev r17988
15:05:26   GEOS: 3.9.0dev-CAPI-1.14.0 
15:05:26   PROJ: 6.2.0
15:05:26 
15:05:26 Running tests
15:05:26 

15:22:17 psql:/var/lib/jenkins/workspace/pg/rel/pg12w64/share/postgresql/contrib/postgis-3.1/postgis.sql:2793: ERROR:  could not find function "postgis_lib_revision" in file "/var/lib/jenkins/workspace/pg/rel/pg12w64/lib/postgresql/postgis-3.so"

15:22:17 make: Leaving directory '/var/lib/jenkins/workspace/postgis/branches/3.0/raster/test/regress'
15:22:17 FAIL: upgrade unpackaged3.1--3.0.1dev

Why are future versions of PostGIS even in past test runs?