vulkan: Disable shared present modes for now

This extension is not yet ratified, and we shouldn't really be
unconditionally exposing the new present modes anyway.

Test: build
Change-Id: I0a9631a5079648c0d8981f07a9f704b7f8758ce3
diff --git a/vulkan/libvulkan/swapchain.cpp b/vulkan/libvulkan/swapchain.cpp
index d1582d1..f4ee375 100644
--- a/vulkan/libvulkan/swapchain.cpp
+++ b/vulkan/libvulkan/swapchain.cpp
@@ -564,8 +564,8 @@
     const VkPresentModeKHR kModes[] = {
         VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_FIFO_KHR,
         // TODO(chrisforbes): should only expose this if the driver can.
-        VK_PRESENT_MODE_SHARED_DEMAND_REFRESH_KHR,
-        VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR,
+        // VK_PRESENT_MODE_SHARED_DEMAND_REFRESH_KHR,
+        // VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR,
     };
     const uint32_t kNumModes = sizeof(kModes) / sizeof(kModes[0]);