zink: update profiles schema

We technically need the 251 version, but the schema for that version
is not released yet, so this is the best we can do.

See https://github.com/KhronosGroup/Vulkan-Profiles/issues/437

This gets rid of some JSON schema-validation warnings.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23308>

src/gallium/drivers/zink/VP_ZINK_requirements.json

@@ -1,5 +1,5 @@
 {
-    "$schema": "https://schema.khronos.org/vulkan/profiles-0.8.1-230.json#",
+    "$schema": "https://schema.khronos.org/vulkan/profiles-0.8.1-250.json",
     "capabilities": {
         "vulkan10requirements": {
             "features": {