fix(ci): deduplicate fleet label validation

[Giselle Rogers (gbrogers)]

Summary

• remove the duplicate package-index validator from the Tests workflow
• keep Validate / validate-package-index as the single fleet-label-aware gate
• avoid stale pre-label failures that only refreshed after closing and reopening a PR

Why

The Tests workflow only responds to the default pull_request activity types, while the duplicate validator depends on PR labels. The canonical Validate workflow already responds to labeled and unlabeled events and is the required status check for staging.

Testing

• node --test scripts/validate-runneth-package-index.mjs (11 passing)
• git diff --check

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge because the removed validation is still performed by the canonical label-aware Validate workflow for pull requests.

The change only removes a duplicate CI job, and the remaining Validate workflow continues to execute the package-index validator on pull-request code and label changes.

_{Reviews (1): Last reviewed commit: "fix(ci): deduplicate fleet label validat..." | Re-trigger Greptile}