Fix ops-recipe test script

[QuentinBisson]

Before adding a new alerting rule into this repository you should consider creating an SLO rules instead.
SLO helps you both increase the quality of your monitoring and reduce the alert noise.

• How to create a SLO rule: https://github.com/giantswarm/sloth-rules#how-to-create-a-slo
• Documentation: https://intranet.giantswarm.io/docs/monitoring/slo-alerting/

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Towards reenabling https://github.com/giantswarm/giantswarm/issues/23638

This PR fixes a few issues:

• After some changes, some rules were rendered containing only comments and this caused issues when running the script jq: error (at <stdin>:1): Cannot iterate over null (null). This fixes the templating by moving the comment after the helm templating.
• This PR also makes sure this script work with ops-recipes under things like cilium/cilium-performance-issues/_index.md. I have tested it with a small modification because the ciliumslow opsrecipe in in the dev-and-releng folder for some weird reasons but here is the output if after I've added the dev-and-releng to the list of ops-recipes:
  file cilium.rules.yml / alert: CiliumAPITooSlow / recipe: cilium/cilium-performance-issues - OK

Checklist

• Update CHANGELOG.md
• Add Unit tests
• Follow Alert structure
• Consider creating a dashboard (guidelines) (if it does not exist already) to help oncallers monitor the status of the issue.
• Request review from oncall area, as well as team (e.g: oncall-kaas-cloud GitHub group).

[QuentinBisson]

@hervenicol I think I could use your eyes :)

[TheoBrigitte]

Maybe explain when we should remove vintage, seems obvious but something like when all vintage installations are gone I think that's what you mean here.