This is the opposite of previous code, which would keep those
'deprecated' overrides arround (often in a dedicated collection), when
they were detected as user-edited.
While this is a safe-ish way to (try to) preserve user-edited data, this
tends to add too much 'trash' data to production scenes, which cleaning
becomes a burden.
Note that user will get warnings in thos cases, and can always choose
not to save the current blend file and go fix the library issue instead.
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