stop using evr container, Katello doesn't need it anymore

Author: evgeni

.github/workflows/unit_tests.yaml

@@ -21,5 +21,4 @@ jobs:
     uses: theforeman/actions/.github/workflows/foreman_plugin.yml@v0
     with:
       plugin: foreman_kernel_care
-      postgresql_container: ghcr.io/theforeman/postgresql-evr
       test_existing_database: false