Force depth writes when fetching shader output in pixel history

* If depth is disabled this will do nothing, but if depth is enabled this
  ensures we actually get the depth value from the fragment.

renderdoc/driver/vulkan/vk_pixelhistory.cpp

@@ -2567,6 +2567,7 @@ struct VulkanPixelHistoryPerFragmentCallback : VulkanPixelHistoryCallback
 
     {
       ds->depthBoundsTestEnable = VK_FALSE;
+      ds->depthWriteEnable = VK_TRUE;
       ds->depthCompareOp = VK_COMPARE_OP_ALWAYS;
     }