fix comment

src/ImageSharp/Common/Helpers/DebugGuard.cs

@@ -27,7 +27,7 @@ namespace SixLabors
         }
 
         /// <summary>
-        /// Verifies whether a condition (indicating disposed state) is met, throwing an ObjectDisposedException if it's false.
+        /// Verifies whether a condition (indicating disposed state) is met, throwing an ObjectDisposedException if it's true.
         /// </summary>
         /// <param name="isDisposed">Whether the object is disposed.</param>
         /// <param name="objectName">The name of the object.</param>