chore(tvix): Use StatusOr API available in Abseil's version

The Abseil version of `StatusOr` does not come with the status macros
or the `Consume*` family of functions.

This change modifies the existing code to use the common denominator
of the API that is available between Abseil's own implementation of
`StatusOr` and the one from Tensorflow that we are currently using.

Change-Id: I5c37f68636a1fd54d153f95d7303ab8644abb774

third_party/nix/src/nix-daemon/nix-daemon-proto.cc

@@ -245,7 +245,7 @@ class WorkerServiceImpl final : public WorkerService::Service {
                           std::string(nar_hash.status().message()));
           }
 
-          info.narHash = nar_hash.ConsumeValueOrDie();
+          info.narHash = *nar_hash;
           for (const auto& ref : path_info.references()) {
             info.references.insert(ref);
           }