Fix Vulkan tests after GrContextFactory move to sk_gpu_test

Fix Vulkan tests after GrContextFactory move to sk_gpu_test

BUG=skia:
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Review URL: https://codereview.chromium.org/1844983003
diff --git a/tests/VkWrapTests.cpp b/tests/VkWrapTests.cpp
index 472664b..382bdbe 100755
--- a/tests/VkWrapTests.cpp
+++ b/tests/VkWrapTests.cpp
@@ -19,6 +19,8 @@
 #include "vk/GrVkMemory.h"
 #include "vk/GrVkTypes.h"
 
+using sk_gpu_test::GrContextFactory;
+
 const int kW = 1024;
 const int kH = 1024;
 const GrPixelConfig kPixelConfig = kRGBA_8888_GrPixelConfig;