Removed support for ingester.statefulset_replicas

[pracucci]

What this PR does:
The issue #209 make me realise the chunks storage with WAL enabled is using a pattern different than any other place in our jsonnet to configure the number of replicas. Instead of fixing #209 applying the config option to blocks storage too, I'm proposing to remove that config option at all, because it's looks like breaking our config consistency.

Which issue(s) this PR fixes:
Fixes #209

Checklist

• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[bboreham]

I tried adding the lines given in the changelog, but I get Unknown variable: statefulSet.
Could you give more context on how they should be used?

[pracucci]

I tried adding the lines given in the changelog, but I get Unknown variable: statefulSet.
Could you give more context on how they should be used?

@bboreham Yes, sure. Something like this:

local statefulSet = $.apps.v1.statefulSet,

ingester_statefulset+:
    statefulSet.mixin.spec.withReplicas(9),