ci: add graphile-postgis to matrix so the ST_GeomFromGeoJSON fix is CI-validated

Author: pyramation

.github/workflows/run-tests.yaml

@@ -73,6 +73,8 @@ jobs:
             env: {}
           - package: graphile/graphile-connection-filter
             env: {}
+          - package: graphile/graphile-postgis
+            env: {}
           - package: graphql/server-test
             env: {}
           - package: graphql/env