Update @gitterhq/services@1.23.0 dependency with other Heroku fixes

Update @gitterhq/services dependency with other Heroku fixes to only generate one event from a completed Heroku app event

• Release new version of @gitterhq/services, 1.23.0
• Update dependency in https://gitlab.com/gitlab-org/gitter/gitter-webhooks-handler and deploy
  • Merge dependency update, https://gitlab.com/gitlab-org/gitter/gitter-webhooks-handler/merge_requests/20
  • Deploy 5.2.0, https://gitlab.com/gitlab-org/gitter/gitter-webhooks-handler/merge_requests/21
• Update dependency in webapp project here

---

cc @wlach