fix rtnetlink compilation

although little-dude/netlink#203 and
little-dude/netlink#202 had no direct
conflict, merging both broke rtnetlink:

```
 error[E0063]: missing field `replace` in initializer of `neighbour::add::NeighbourAddRequest`
  --> rtnetlink/src/neighbour/add.rs:58:9
   |
58 |         NeighbourAddRequest { handle, message }
   |         ^^^^^^^^^^^^^^^^^^^ missing `replace`
```

src/neighbour/add.rs

@@ -55,7 +55,11 @@ impl NeighbourAddRequest {
 
         message.nlas.push(Nla::LinkLocalAddress(lla.to_vec()));
 
-        NeighbourAddRequest { handle, message }
+        NeighbourAddRequest {
+            handle,
+            message,
+            replace: false,
+        }
     }
 
     /// Set a bitmask of states for the neighbor cache entry.