build: drop redundant direct graphile-postgis dependency

ConstructivePreset → GraphilePostgisPreset already pulls graphile-postgis
in transitively, and nothing in this package imports it directly after
the previous commit removed the explicit plugin registration. Dropping
the direct dep in packages/integration-tests/package.json.

Tests still 36/36.

Author: pyramation

packages/integration-tests/package.json

@@ -25,8 +25,5 @@
     "graphql": "16.13.0",
     "pgsql-test": "^4.7.6",
     "typescript": "^5.9.3"
-  },
-  "dependencies": {
-    "graphile-postgis": "2.11.0"
   }
 }