msglist test [nfc]: Add distinct ids to messages in 'show names on DM…

…s' setup

This will prevent a future test failure when other parts of
the app begin assuming that messages have unique ids.

test/widgets/message_list_test.dart

@@ -212,9 +212,9 @@ void main() {
 
     testWidgets('show names on DMs', (tester) async {
       await setupMessageListPage(tester, messages: [
-        eg.dmMessage(from: eg.selfUser, to: []),
-        eg.dmMessage(from: eg.otherUser, to: [eg.selfUser]),
-        eg.dmMessage(from: eg.thirdUser, to: [eg.selfUser, eg.otherUser]),
+        eg.dmMessage(id: 1, from: eg.selfUser, to: []),
+        eg.dmMessage(id: 2, from: eg.otherUser, to: [eg.selfUser]),
+        eg.dmMessage(id: 3, from: eg.thirdUser, to: [eg.selfUser, eg.otherUser]),
       ]);
       store.addUser(eg.otherUser);
       store.addUser(eg.thirdUser);