Fix VK_Descriptor_Index test declaring too large array

* This was variably sized so in practice we didn't use it, but the spec still
  requires us to respect the max sizes that could be used for the upper bound
  and this lead to the wrong texture being sampled on NV.

util/test/demos/vk/vk_descriptor_index.cpp

@@ -372,7 +372,8 @@ void main()
                 {
                     4,
                     VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER,
-                    UINT32_MAX,
+                    1000000,    // this must still be under the maxDescriptorSet* counts even though
+                                // we'll trim this massively on allocation
                     VK_SHADER_STAGE_FRAGMENT_BIT | VK_SHADER_STAGE_COMPUTE_BIT,
                 },
             })