Remove ToString() which could give null exception

If property is null, its string interpolation will just be blank.

src/JuliusSweetland.OptiKey/App.xaml.cs

@@ -277,7 +277,7 @@ private void logUserSettings()
 
                 foreach (SettingsProperty property in Settings.Default.Properties)
                 {
-                    Log.InfoFormat("  {0}: {1}", property.Name, Settings.Default[property.Name].ToString());
+                    Log.InfoFormat("  {0}: {1}", property.Name, Settings.Default[property.Name]);
                 }
             }
         }