Fix hans image and title

public/dialogs/hans.json

 {
   "$schema": "../../src/dialogSet.schema.json",
-  "title": "Stefan Dißmann – Geschäftsleitung",
-  "imageUrl": "./images/StefanDissmann300dpi3.jpg",
+  "title": "Hans Decker",
+  "imageUrl": "./images/portrait_decker.png",
   "startDialogName": "start",
   "dialogs": {
     "start": {