update Ditto version in Helm chart to 3.6.4

Author: thjaeckle

deployment/helm/ditto/Chart.yaml

@@ -17,7 +17,7 @@ description: |
   (real world “Things”, e.g. devices like sensors, smart heating, connected cars, smart grids, EV charging stations etc).
 type: application
 version: 3.6.4  # chart version is effectively set by release-job
-appVersion: 3.6.3
+appVersion: 3.6.4
 keywords:
   - iot-chart
   - digital-twin