Update (fixed now)

Expected Behaviour

Label xmldoc should be added to the update PRs created by the bot which update xmldoc dependency.

Current Behaviour

Getting a invalid configuration warning.

Cause

https://github.com/renovatebot/renovate/blob/d88debdcc0064c3893509ed36d6aaff45919bccc/lib/config/migrations/custom/package-rules-migration.ts#L70-L76

matchPackagePrefixes only gets migrated to matchpackageNames if its an array. But in out case its a string, in which it just gets deleted from the package rule.

Possible Fix

Migrate strings too.