fix: update out of sync Prometheus image

[hsmatulis]

The prometheus image in the example directory should be kept in sync with the one used by the 0.17 branch

[bwplotka]

this is ideally bumped too, as mentioned in https://github.com/GoogleCloudPlatform/prometheus-engine/pull/1786/files#r2461450478

[bwplotka]

Can we quickly hook it with /charts while we are here?

[bwplotka]

Thanks, added some comments. Also not sure if docs should link to unreleased 0.17 branch/release at the moment or should we just use main. Let's chat

Also please update commit msg, that's why conform is complaining.

FYI, have you seen #1786?

Nevertheless let's converge to something that will work for docs. I'd say .6 image with config-reloader bump and doing this on 0.15 release might be best for now (let's discuss in gchat), but I wonder if there's a room for special branch for docs or at least minimal templating for basics like config-reloader version.

[bwplotka]

So the issue, as mentioned in our docs, is the unfortunate cycle: Our repos is the source for building but also contain examples and outputs to use ONCE things are built and deployed. This image does not exists until we release things to GKE. Louhi flow only builds to staging. This is a major pain, but there's not much we can do, unless we want to show staging here OR some automation for creating PRs once we have GKE prod images.

That's why @lyanco changed to bit older image in #1786

[bwplotka]

Looking on prod registry, I see .6 which is probably the best we can share now.

Suggested change

	image: gke.gcr.io/prometheus-engine/prometheus:v2.53.5-gmp.0-gke.8
	image: gke.gcr.io/prometheus-engine/prometheus:v2.53.5-gmp.0-gke.6