change: Error sending greet dm will now be a warning

change: initial canvas price down to 3 from 10, 10 is way too expensive

src/NadekoBot/Modules/Administration/GreetBye/GreetService.cs

@@ -339,7 +339,7 @@ public class GreetService : INService, IReadyExecutor
         }
         catch (Exception ex)
         {
-            Log.Error(ex, "Error sending greet dm");
+            Log.Warning(ex, "Unable to send Greet DM. Probably the user has closed DMs");
             return false;
         }