Update vulkan format features in caps.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1847963003

Review URL: https://codereview.chromium.org/1847963003
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index de1e905..55f1eae 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -650,8 +650,7 @@
 
     int samples = rt->numStencilSamples();
 
-    SkASSERT(this->vkCaps().stencilFormats().count());
-    const GrVkCaps::StencilFormat& sFmt = this->vkCaps().stencilFormats()[0];
+    const GrVkCaps::StencilFormat& sFmt = this->vkCaps().preferedStencilFormat();
 
     GrVkStencilAttachment* stencil(GrVkStencilAttachment::Create(this,
                                                                  GrGpuResource::kCached_LifeCycle,