Mention the reaplcement to compound types in Overview - Dropped Constructs section

Author: ShapelessCat

docs/docs/reference/overview.md

@@ -87,7 +87,7 @@ These constructs are proposed to be dropped without a new construct replacing th
 - [Symbol literals](dropped-features/symlits.md),
 - [Auto application](dropped-features/auto-apply.md),
 - [Weak conformance](dropped-features/weak-conformance.md),
-- [Compound types](new-types/intersection-types.md),
+- [Compound types](new-types/intersection-types.md) (replaced by [Intersection types](new-types/intersection-types.md)),
 - [Auto tupling](https://github.com/lampepfl/dotty/pull/4311) (implemented, but not merged).
 
 The date when these constructs are dropped varies. The current status is: