Update status section in adr-005-box-sx.md (#7204)

Author: lesliecdubs

contributor-docs/adrs/adr-005-box-sx.md

@@ -2,10 +2,9 @@
 
 ## Status
 
-| Stage    | Status |
-| -------- | ------ |
-| Approved | ✅     |
-| Adopted  | 🚧     |
+| Stage  | State                                                                                                      |
+| ------ | ---------------------------------------------------------------------------------------------------------- |
+| Status | Superseded by [CSS ADR](https://github.com/primer/react/blob/main/contributor-docs/adrs/adr-016-css.md) ⚠️ |
 
 ## Context