Fix accidental doulbe negation instance.md

tutorial/book/src/setup/instance.md

@@ -146,7 +146,7 @@ let info = vk::InstanceCreateInfo::builder()
     .flags(flags);
 ```
 
-This code enables `KHR_PORTABILITY_ENUMERATION_EXTENSION` if your application is being compiled for a platform that lacks a non-conformant Vulkan implementation (just checking for macOS here) and the Vulkan version meets or exceeds the minimum version we just defined.
+This code enables `KHR_PORTABILITY_ENUMERATION_EXTENSION` if your application is being compiled for a platform that lacks a conformant Vulkan implementation (just checking for macOS here) and the Vulkan version meets or exceeds the minimum version we just defined.
 
 This code also enables `KHR_GET_PHYSICAL_DEVICE_PROPERTIES2_EXTENSION` under the same conditions. This extension is needed to enable the `KHR_PORTABILITY_SUBSET_EXTENSION` device extension which will be added later in the tutorial when we set up a logical device.