fix(helm): add livenessProbe to read pods in Simple Scalable mode

[someStrangerFromTheAbyss]

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #15191
Special notes for your reviewer:
This mainly add livenessProbe for the read pod. This will maybe helm some issues with the read pods when deploying a loki in simple Scalable mode

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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