software/erp5: fix schema definition of test-runner key

The schema was not matching implementation (it was not even correct
schema)

software/erp5/instance-erp5-input-schema.json

@@ -362,7 +362,6 @@
         "$ref": "../caucase/instance-caucase-input-schema.json"
       },
       "type": "object"
-    }
     },
     "test-runner": {
       "description": "Test runner parameters.",
@@ -385,4 +384,5 @@
       },
       "type": "object"
     }
+  }
 }