chore: use file-scoped namespace

src/Shared/Microsoft.Windows.Shell/Standard/AC.cs

@@ -1,10 +1,9 @@
 using System;
 
-namespace Standard
+namespace Standard;
+
+internal enum AC : byte
 {
-    internal enum AC : byte
-    {
-        SRC_OVER,
-        SRC_ALPHA
-    }
-}
+    SRC_OVER,
+    SRC_ALPHA
+}