upgrade to latest stable rabbitmq

[supersven]

Use latest stable RabbitMQ version (3.13.7) and Helm chart (14.6.9) - one is implied by the other.

This is compatible to our backend:

• I ran tests locally against a docker-compose deployment
• The Helmfile deployment for the CI test runs uses the chart: https://github.com/wireapp/wire-server/blob/sventennie%2Fupgrade-to-latest-stable-rabbitmq/hack/helmfile.yaml#L160

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[lwille]

⚠️ side note: as this is a major version upgrade, I think we should to communicate this as well as upgrade instructions to the users of our chart.

[supersven]

⚠️ side note: as this is a major version upgrade, I think we should to communicate this as well as upgrade instructions to the users of our chart.

Thanks a lot 👍 That's a good one. I'll add that to the release notes.

[lwille]

Thanks a lot 👍 That's a good one. I'll add that to the release notes.

Right, the major version upgrade is just in the Helm chart, not in RabbitMQ -- however, there must be reasons for a new major xD