Validate yaml returns different results

[CIGbalance]

This is actually not needed any more, the update existing data also validates already

[Copilot]

Pull request overview

Fixes merge_yaml.py’s post-merge validation step by removing an incorrect call pattern to validate_yaml(...) (which is implemented as a CLI-style function that exits the process rather than returning data), avoiding inconsistent/incorrect “return value” behavior during merges.

Changes:

• Removed the final “validate resulting data” block after writing the merged YAML.
• Relies on the existing in-memory validate_data(...) check performed before writing merged output.

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