[Fuchsia] Use the trusted certs in the image

runtime/runtime_args.gni

Index: runtime/runtime_args.gni
diff --git a/runtime/runtime_args.gni b/runtime/runtime_args.gni
index 52b2407ad79e953ef37e0f1ad1f414a480153766..750c2b4346b3dab460770e9b4c667f1d738f7d60 100644
--- a/runtime/runtime_args.gni
+++ b/runtime/runtime_args.gni
@@ -17,8 +17,3 @@ declare_args() {
   # the VM enables this only for Linux builds.
   dart_use_tcmalloc = false
 }
-
-# TODO(zra): Remove this when Fuchsia has a root cert cache on the filesystem.
-if (defined(is_fuchsia) && is_fuchsia) {
-  dart_use_fallback_root_certificates = true
-}