Remove EF query warnings from test runs

GameList.Tests/VoteTests.cs

@@ -98,7 +98,7 @@ public class VoteTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.DisplayName = null;
             await db.SaveChangesAsync();
         });