Update third-party lockfile's cxx-gen to the repo version
diff --git a/third-party/Cargo.lock b/third-party/Cargo.lock
index 8aa5a1f..199064b 100644
--- a/third-party/Cargo.lock
+++ b/third-party/Cargo.lock
@@ -85,7 +85,7 @@
 
 [[package]]
 name = "cxx-gen"
-version = "0.0.1"
+version = "0.4.0"
 dependencies = [
  "cc",
  "codespan-reporting",