charts/promscale: propagate alerts fixes from upstream

[paulfantom]

What this PR does / why we need it

Propagating changes from https://github.com/timescale/promscale/pull/1773

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer

Checklist

• [ ] Chart Version bumped
• [ ] CLA signed