ethernet: fix nullability annotations

Remove a couple of outdated annotations. Both capabilities and IP configuration are guaranteed to be NonNull. There is no need to add a @NonNull annotation as in general, non-nullability is inferred unless marked otherwise.

Change-Id: I75a1d8db23e022134cd805e04e108db3e24d016b
Test: TH
Bug: 257406736
diff --git a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
index 00f6c56..0605abe 100644
--- a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
+++ b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
@@ -269,10 +269,10 @@
         private final Set<Integer> mRequestIds = new ArraySet<>();
 
         private volatile @Nullable IpClientManager mIpClient;
-        private @NonNull NetworkCapabilities mCapabilities;
+        private NetworkCapabilities mCapabilities;
         private @Nullable EthernetIpClientCallback mIpClientCallback;
         private @Nullable EthernetNetworkAgent mNetworkAgent;
-        private @Nullable IpConfiguration mIpConfig;
+        private IpConfiguration mIpConfig;
 
         /**
          * A map of TRANSPORT_* types to legacy transport types available for each type an ethernet