Fix wrong options in readme

Author: SaschaWillems

README.adoc

@@ -1,5 +1,5 @@
 ////
-- Copyright (c) 2019-2025, Arm Limited and Contributors
+- Copyright (c) 2019-2026, Arm Limited and Contributors
 -
 - SPDX-License-Identifier: Apache-2.0
 -
@@ -158,12 +158,12 @@ vulkan_samples sample swapchain_images
 # Run AFBC sample in benchmark mode for 5000 frames
 vulkan_samples sample afbc --benchmark --stop-after-frame 5000
 
-# Run compute nbody using headless_surface and take a screenshot of frame 5 
-# Note: headless_surface uses VK_EXT_headless_surface.
+# Run compute nbody using headless-surface and take a screenshot of frame 5 
+# Note: headless-surface uses VK_EXT_headless_surface.
 # This will create a surface and a Swapchain, but present will be a no op.
 # The extension is supported by Swiftshader(https://github.com/google/swiftshader).
 # It allows to quickly test content in environments without a GPU.
-vulkan_samples sample compute_nbody --headless_surface -screenshot 5
+vulkan_samples sample compute_nbody --headless-surface --screenshot 5
 
 # Run all the performance samples for 10 seconds in each configuration
 vulkan_samples batch --category performance --duration 10