Update next.md

Author: sylvestre

next.md

@@ -40,3 +40,4 @@ This file documents the pending improvements or regression:
 * https://github.com/uutils/coreutils/pull/9663
 * https://github.com/uutils/coreutils/pull/10155
 * https://github.com/uutils/coreutils/pull/10156
+* https://github.com/uutils/coreutils/pull/9821