add valid date-check marker

Author: tshepang

src/doc/rustc-dev-guide/src/parallel-rustc.md

@@ -1,8 +1,9 @@
 # Parallel Compilation
 
 <div class="warning">
-Parallel front-end is currently (as of 2024 November) undergoing significant
-changes, this page contains quite a bit of outdated information.
+As of <!-- date-check --> November 2024,
+the parallel front-end is undergoing significant changes,
+so this page contains quite a bit of outdated information.
 
 Tracking issue: <https://github.com/rust-lang/rust/issues/113349>
 </div>