fix(nextclade): remove invalid qc scoreWeight fields

[ivan-aksamentov]

Remove scoreWeight from qc.missingData and qc.mixedSites in the Nextclade dataset config (source and committed output).

The scoreWeight property is not defined on QcRulesConfigMissingData or QcRulesConfigMixedSites in the pathogen.json schema and is silently ignored. It is valid on snpClusters, frameShifts, and stopCodons (those are left unchanged).

• Remove qc.missingData.scoreWeight from source and committed output
• Remove qc.mixedSites.scoreWeight from source and committed output

⚠️ The existing dataset in nextclade_data is already patched in nextstrain/nextclade_data#440, so no immediate resubmission is needed. But without this upstream fix, the invalid fields will reappear on the next dataset submission from this workflow.

ℹ️ See pathogen.json schema for the QcRulesConfigMissingData and QcRulesConfigMixedSites definitions.

1. Related to: fix: update wnv dataset schema fields nextclade_data#440