Reversion to 'metal' from 'metallic'?

Suggested by Dunkhan here: https://github.com/CleverRaven/Cataclysm-DDA/pull/7869

'Metal' may be the correct adjective to use after all, since it refers specifically to objects made entirely of metal, as opposed to the broader adjective, 'metallic'. It would be nice to hear some more opinions in any case. This PR is here in case 'metal' is preferred.