Proposal : Update Series Giant Robo original source

Proposal details

This proposal will make the following change(s):

Update the original source of the series Giant Robo

Change the original source from Unknown to Manga

Based on the following reason: Missing

With the source: https://myanimelist.net/anime/2321/Giant_Robo_the_Animation__Chikyuu_ga_Seishi_Suru_Hi