DPL-nnn Remove print_list from global scope

[JamesGlover]

Describe the Housekeeping

https://github.com/sanger/samples_extraction/blob/3831e306b18c48d6074846669895e81d215eb99a/app/models/printables/print_asset.rb#L1-L16

This method is defined on Object. I think we can just remove it (couldn't find any calls to it), but if not it should be moved to somethign appropriate.

Blocking issues
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Additional context
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