Added condition="Ready" label to kube_node_status_condition in raw_slo_requests recording rule expression since we only check that condition in the errors.

Without this the slo_error_per_request are 1/5 of the actual value, since the condition label has 5 possible values (Ready, DiskPressure, MemoryPressure, PIDPressure, NetworkUnavailable).

Towards: https://github.com/giantswarm/giantswarm/issues/27921#issuecomment-1804147257

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).