Use vals --decode-kubernetes-secrets

[jkroepke]

What this PR does / why we need it:

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:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (91fceed) 86.67% compared to head (3841e52) 86.67%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #391   +/-   ##
=======================================
  Coverage   86.67%   86.67%           
=======================================
  Files          23       23           
  Lines         833      833           
=======================================
  Hits          722      722           
  Misses        111      111           

Files Changed	Coverage Δ
scripts/commands/post-renderer.sh	100.00% <100.00%> (ø)
scripts/lib/backends/vals.sh	90.00% <100.00%> (ø)

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