Operator ignores Thanos images specified in the CR

In [my CR](https://github.com/operate-first/apps/blob/master/observatorium/base/instance/observatorium.yaml#L50), I have tried setting the image for Thanos Components (Store/Compact/Receive/...) to `quay.io/thanos/thanos:v0.20.1` or any other image but It always uses `quay.io/thanos/thanos:v0.17.1`.