This primarly fixes a breaking change where the MinIO chart
dependency had been reset to the prior, deprecated Chart, which
broke the installation of this Chart from source.
This occured as part of this PR: https://github.com/grafana/helm-charts/pull/2384


presumably due to a failure to rebase between initial raising and
merging.

Have also updated the GET version from 2.1.0 to 2.2.1, inline
with latest release.

Fully E2E tested via GET k8s cluster, with Grafana and GrAgent setup.

Signed-off-by: Heds Simons <hedley.simons@grafana.com>