chore: update changelog with new release

Author: adriencaccia

debian/changelog

@@ -1,3 +1,9 @@
+valgrind (1:3.21.0-0codspeed2) UNRELEASED; urgency=medium
+
+  * Ship prebuilt binaries for arm64
+
+ -- Adrien Cacciaguerra <adrien@codspeed.io>  Thu, 12 Sep 2024 14:30:13 +0000
+
 valgrind (1:3.21.0-0codspeed1) UNRELEASED; urgency=medium
 
   * Merge 3.21.0 from valgrind upstream
@@ -2672,4 +2678,3 @@ valgrind (0.0.20020224-1) unstable; urgency=low
   * Initial Release (closes: #135718)
 
  -- Cyrille Chepelov <cyrille@chepelov.org>  Mon, 25 Feb 2002 20:16:46 +0100
-