CI Linux: fixed failed run (Vulkan)

fixed failed run:
<https://github.com/CESNET/UltraGrid/actions/runs/7002907554/job/19047571995>

Vulkan-Loader seem to be (temporarily?) incompatible with current Vulkan
Headers, which suffix VK_DEBUG_REPORT_OBJECT_TYPE_CUDA_FUNCTION_NV with
_EXT in v1.3.271.

.github/scripts/Linux/install_others.sh

@@ -80,7 +80,8 @@ install_pipewire() {(
 
 # FFmpeg master needs at least v1.3.238 as for 23th Aug '23
 install_vulkan() {(
-        git clone --depth 1 https://github.com/KhronosGroup/Vulkan-Headers
+        git clone --depth 1 -b v1.3.270 \
+                https://github.com/KhronosGroup/Vulkan-Headers
         mkdir Vulkan-Headers/build
         cd Vulkan-Headers/build
         cmake ..