chore: use file-scoped namespace

src/Shared/Microsoft.Windows.Shell/Standard/DWMFLIP3D.cs

@@ -1,11 +1,10 @@
 using System;
 
-namespace Standard
+namespace Standard;
+
+internal enum DWMFLIP3D
 {
-    internal enum DWMFLIP3D
-    {
-        DEFAULT,
-        EXCLUDEBELOW,
-        EXCLUDEABOVE
-    }
-}
+    DEFAULT,
+    EXCLUDEBELOW,
+    EXCLUDEABOVE
+}