Fix chat assertion

petshop-api.postman_collection.json

@@ -2590,7 +2590,8 @@
                   "    pm.response.to.have.status(201);",
                   "});",
                   "var jsonData = pm.response.json();",
-                  "pm.expect(jsonData.senderRole).to.eql('STAFF');"
+                  "pm.expect(jsonData.senderId).to.exist;",
+                  "pm.expect(jsonData.content).to.eql('Reply from Postman');"
                 ]
               }
             }