Fix broken documentation in Connectivity

EthernetManager is @SystemApi, so cannot be referenced from public
API.

Bug: 303184203
Test: m docs
Change-Id: Ib5cc07c89b4ecfdeae704da131ebb307816e35fa

framework-t/src/android/net/EthernetNetworkSpecifier.java

@@ -26,8 +26,6 @@ import java.util.Objects;
 
 /**
  * A {@link NetworkSpecifier} used to identify ethernet interfaces.
- *
- * @see EthernetManager
  */
 public final class EthernetNetworkSpecifier extends NetworkSpecifier implements Parcelable {