[memcached] version bumped to 1.6.31-alpine3.20

[businessbean]

• Memcached 1.6.31 Release Notes
• added alpine version tag to enforce exactly this version
• version info added to labels
  • to allow gatekeeper rules based on them
• old (non-standard) labels removed
• chart version bumped

label example

labels:
  app.kubernetes.io/name: memcached
  app.kubernetes.io/instance: keystone-memcached
  app.kubernetes.io/component: memcached-deployment-kvstore
  app.kubernetes.io/part-of: keystone
  app.kubernetes.io/version: 1.6.31
  app.kubernetes.io/managed-by: "helm"
  helm.sh/chart: memcached-0.6.0

removed labels

labels:
   app: keystone-memcached
   component: memcached
   chart: "memcached-0.5.3"
   release: "keystone"
   heritage: "Helm"
   type: configuration
   application: keystone