Update blog posts with instructions to deploy prometheus-operator, to…

[objectiser]

… explain that no longer required

[objectiser]

@theute @pilhuhn Have added a note block to indicate prom-operator no longer required - or would it be better to update the instructions to no longer refers to it?

[pilhuhn]

I think what is a bit problematic is that there is the note and then 2 lines in the code block (without comment on the line) where people may just copy&paste those.
But then I guess it does no harm if prom-operator is deployed either.

But then those are blog posts with a date, so the note may just be fine. For documentation (not blog) I'd say remove the problematic line.

[objectiser]

+1 documentation should not reference prom-operator.

So is it ok to merge as is?