(docs) Fix Fern Editor redirect (#1103)

Author: devalog

fern/docs.yml

@@ -416,7 +416,7 @@ redirects:
   - source: /learn/docs/navigation/changelogs
     destination: /learn/docs/customization/changelogs
     permanent: true
-  - source: /learn/docs/content/visual-editor
+  - source: /learn/docs/writing-content/visual-editor
     destination: /learn/docs/writing-content/fern-editor
     permanent: true
   - source: /learn/docs/writing-content/code-blocks