[examples][media] fix compiling use_aac_decoder_test

In order to get this code to compile, I needed to depend on
the gtest_main target.

Change-Id: Ide525adc88b4e5ba931fd9aa4bb3b5c683e1cecc
diff --git a/garnet/examples/media/use_media_decoder/BUILD.gn b/garnet/examples/media/use_media_decoder/BUILD.gn
index 7627d75..1e8fae3 100644
--- a/garnet/examples/media/use_media_decoder/BUILD.gn
+++ b/garnet/examples/media/use_media_decoder/BUILD.gn
@@ -35,7 +35,6 @@
     "//garnet/public/lib/ui/base_view/cpp",
     "//garnet/public/lib/ui/scenic/cpp",
     "//src/media/audio/lib/wav_writer:wav_writer",
-    "//third_party/googletest:gtest",
     "//zircon/public/lib/async",
     "//zircon/public/lib/async-cpp",
   ]
@@ -65,6 +64,7 @@
 
   deps = [
     ":use_media_decoder_source_set",
+    "//third_party/googletest:gtest_main",
   ]
 }