Change kExampleData in metadata_test.cc to const

Example data for lookup in metadata_test.cc should be const now that
metadata API allows it.

BUG=aomedia:2507

Change-Id: Ic19916ab47024cecfa78402bc866cfb10a7d7d11
diff --git a/test/metadata_test.cc b/test/metadata_test.cc
index e7ddc0f..4bf9595 100644
--- a/test/metadata_test.cc
+++ b/test/metadata_test.cc
@@ -13,8 +13,7 @@
 
 namespace {
 const size_t kExampleDataSize = 10;
-// TODO(daniel.vt@samsung.com): Make this const when the metadata API allows it.
-uint8_t kExampleData[kExampleDataSize] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+const uint8_t kExampleData[kExampleDataSize] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
 
 #if CONFIG_AV1_ENCODER