Don't reverse stack trace when showing

When debugging nix expressions the outermost trace tends to be more useful
than the innermost. It is therefore printed last to save developers from
scrolling.

src/libutil/error.cc

@@ -287,7 +287,7 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
 
     // traces
     if (showTrace && !einfo.traces.empty()) {
-        for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter) {
+        for (auto iter = einfo.traces.begin(); iter != einfo.traces.end(); ++iter) {
             oss << "\n" << "… " << iter->hint.str() << "\n";
 
             if (iter->pos.has_value() && (*iter->pos)) {