Fix compile warning due to unused variable binding.

We still need the check, since we don't have narinfo for locally built store paths.

src/nix/path-info.cc

@@ -54,7 +54,7 @@ static json pathInfoToJSON(
 
                 jsonObject["closureSize"] = getStoreObjectsTotalSize(store, closure);
 
-                if (auto * narInfo = dynamic_cast<const NarInfo *>(&*info)) {
+                if (dynamic_cast<const NarInfo *>(&*info)) {
                     uint64_t totalDownloadSize = 0;
                     for (auto & p : closure) {
                         auto depInfo = store.queryPathInfo(p);