Update announcement of removal of Arena-enabled constructors for Repeated/Map fields in 2025-09-19 news.

PiperOrigin-RevId: 820781794

Author: ClaytonKnittel

content/news/2025-09-19.md

@@ -25,6 +25,9 @@ be removed and their behavior will become the default:
 *   `PROTOBUF_FUTURE_REMOVE_ADD_IGNORE_CRITERIA`
 *   `PROTOBUF_FUTURE_STRING_VIEW_DESCRIPTOR_DATABASE`
 *   `PROTOBUF_FUTURE_NO_RECURSIVE_MESSAGE_COPY`
+*   `PROTOBUF_FUTURE_REMOVE_REPEATED_PTR_FIELD_ARENA_CONSTRUCTOR`
+*   `PROTOBUF_FUTURE_REMOVE_MAP_FIELD_ARENA_CONSTRUCTOR`
+*   `PROTOBUF_FUTURE_REMOVE_REPEATED_FIELD_ARENA_CONSTRUCTOR`
 
 ### New RepeatedPtrField Layout {#cpp-repeatedptrfield-layout}
 
@@ -39,9 +42,12 @@ arena-safe counterparts and be deprecated.
 Protobufs will be hardened against OOB errors by adding comprehensive bounds
 checking to repeated field accesses.
 
-### Remove Arena Pointers from Repeated Fields {#cpp-remove-arena-pointers}
+<a id="cpp-remove-arena-pointers"></a>
 
-The `RepeatedPtrField(Arena*)` constructor will be deleted.
+### Remove Arena-enabled constructors from Repeated/Map Fields {#cpp-remove-arena-ctors}
+
+The `RepeatedField(Arena*)`, `RepeatedPtrField(Arena*)`, and `Map(Arena*)`
+constructors will be deleted.
 
 ### Remove Deprecated APIs {#cpp-remove-apis}