Apply suggestions from code review

Co-authored-by: Léo Valais <[email protected]>

content/docs/reference/design-docs/rolling-stock-collections.en.md

@@ -21,14 +21,13 @@ These issues are deemed too damaging to implement rolling stock authorization as
 
 A concept of rolling stock collection would be introduced:
 - each rolling stock must belong to exactly one collection
-- rolling stocks do not have individual permissions. permissions are managed at the collection level
+- rolling stocks do not have individual permissions; permissions are managed at the collection level
 - when creating a scenario, rolling stock collections need to be added
 
 Rolling stock collections have:
 - a name
 - a description
 
-Rolling stocks belong to a collection.
 
 ## Implementation plan