slightly reverted AmbientValueAttribute\Overview\attributesdemocontrol.cs so that Designer can work

BTW I also edited Issue dotnet#10961 to include this Designer failure

Author: Dick Baker

.gitignore

@@ -326,3 +326,4 @@ _dependentPackages/
 /snippets/csharp/System.ComponentModel/AsyncCompletedEventArgs/Overview/primenumbercalculatormain.resx
 /snippets/csharp/System.ComponentModel/BackgroundWorker/Overview/fibonacciform.resx
 /snippets/csharp/System.ComponentModel/Dick.bat
+/snippets/csharp/System.ComponentModel/AmbientValueAttribute/Overview/attributesdemocontrol.resx