Missing IHO bibliography edition number for B-7

[ronaldtse]

• B-7 (which is GEBCO) and doesn't seem to have a particular edition anymore

@iho-ohi could you help provide some information for B-7 editions? Thanks!

Originally posted by @ronaldtse in https://github.com/relaton/relaton-data-iho/issues/20#issuecomment-2208711784

[iho-ohi]

B-7 no longer exists. The document has been withdrawn.