Fix 4 external code table links to ensure link concatenates with value to form correct ID

Created by: un-cefact-github-app[bot]

Updated external code-tables with their relevant joining characters that are used on the respective external sites. See https://github.com/uncefact/spec-untp/issues/369 for more.

In particular, this PR updates three GS1 external codes (BizStep, DISP, and BTT) so their URL link includes the trailing hyphen - to form the correct enumeration values (but see note below about now incorrect link in description to users), as well as a uncefact UnitOfMeasure external code with its trailing hash #.

Note: Jargon uses the URL both for concatenating with a value for an ID and for displaying to the user as the link where they can see all values, but it can't work for both always. This change gives priority to the former (valid and usable jsonld, with possibly incorrect link in JSONSchema description to users). See https://github.com/jargon-sh/issues/issues/52