Add regression issue number to Misc/NEWS entry.
diff --git a/Misc/NEWS b/Misc/NEWS
index 77d6eb9..ea649be 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,10 +10,10 @@
 Core and Builtins
 -----------------
 
-- Backout issue #1856 patch (avoid crashes and lockups when daemon threads
-  run while the interpreter is shutting down; instead, these threads are
-  now killed when they try to take the GIL), as it seems to break some
-  existing code.
+- Issue #21963: backout issue #1856 patch (avoid crashes and lockups when
+  daemon threads run while the interpreter is shutting down; instead, these
+  threads are now killed when they try to take the GIL), as it seems to
+  break some existing code.
 
 - Issue #22604: Fix assertion error in debug mode when dividing a complex
   number by (nan+0j).