Adjust a comment

Author: grynspan

Sources/Testing/Attachments/Images/Attachment+AttachableAsImage.swift

@@ -106,7 +106,11 @@ extension Attachment {
 #endif
 @available(_uttypesAPI, *)
 extension Attachment where AttachableValue: AttachableWrapper, AttachableValue.Wrapped: AttachableAsImage {
-  /// The image format to use when encoding the represented image.
+  /// The image format to use when encoding the represented image, if specified.
+  ///
+  /// @Metadata {
+  ///   @Available(Swift, introduced: 6.3)
+  /// }
   @_disfavoredOverload public var imageFormat: AttachableImageFormat? {
     // FIXME: no way to express `where AttachableValue == _AttachableImageWrapper<???>` on a property (see rdar://47559973)
     (attachableValue as? _AttachableImageWrapper<AttachableValue.Wrapped>)?.imageFormat