Fix typo in test

Author: grynspan

Tests/TestingTests/AttachmentTests.swift

@@ -853,7 +853,7 @@ extension AttachmentTests {
 #if canImport(CoreGraphics) && canImport(_Testing_CoreGraphics)
       let format3 = AttachableImageFormat(contentType: .tiff)
 #elseif canImport(WinSDK) && canImport(_Testing_WinSDK)
-      let format3 = AttachableImageFormat(encoderCLSID: .CLSID_WICTiffEncoder)
+      let format3 = AttachableImageFormat(encoderCLSID: CLSID_WICTiffEncoder)
 #endif
       #expect(format1 == format1)
       #expect(format2 == format2)