Update fast_guassian_test for the new sizes

Change-Id: I8905fc3618bebda32097185b2fab32579b96604c
diff --git a/y2020/vision/sift/fast_gaussian_test.cc b/y2020/vision/sift/fast_gaussian_test.cc
index e62f26e..20a56f7 100644
--- a/y2020/vision/sift/fast_gaussian_test.cc
+++ b/y2020/vision/sift/fast_gaussian_test.cc
@@ -47,7 +47,7 @@
 
 // Verifies that FastGaussian and cv::GaussianBlur give the same result.
 TEST_F(FastGaussianTest, FastGaussian) {
-  const auto image = RandomImage(360, 640, CV_16SC1);
+  const auto image = RandomImage(480, 640, CV_16SC1);
   cv::Mat slow, fast, fast_direct;
   static constexpr double kSigma = 1.9465878414647133;
   static constexpr int kSize = 13;