Update Chart.yaml to apiVersion: v2

Our Chart.yaml is currently using apiVersion: v1, but the latest is v2:

https://helm.sh/docs/topics/charts/#the-apiversion-field

Changes from v1 to v2:

• A dependencies field defining chart dependencies, which were located in a separate requirements.yaml file for v1 charts (see Chart Dependencies).
• The type field, discriminating application and library charts (see Chart Types).

See also

• An example where Helm v3 was used with auto-deploy-app, which caused an issue: 3fb943be (comment 277053965)