docs: Migrationsdokument haelt das Vorher fest und verweist auf die .template-Form, Rest-Abschnitt aus types/source.md entfernt (#107)

Files changed:
- CHANGES.md
- VERSION
- instructions/migrate-corpus.md
- instructions/migrations/6.0.0-type-guidance-split.md
- types/source.md

types/source.md

@@ -44,10 +44,6 @@ how to write a conforming page is [types/source.guidance.md](source.guidance.md)
 | `concepts` | No | Titles of the concepts mentioned in this source |
 | `summary` | Yes | One-liner for `kb/index.md` |
 
-## Authoring guidance
-
-- The title starts with "Source - ", followed by the name of the source
-
 ## Template
 
 The block below is page material, so it is written in this instance's KB language