btrfs-progs: update CHANGES for 6.8.1

Signed-off-by: David Sterba <dsterba@suse.com>

CHANGES

@@ -13,6 +13,23 @@ btrfs-progs-6.8 (2024-03-26)
       * error handling fixes
       * cleanups and refactoring
 
+btrfs-progs-6.8.1 (2024-05-02)
+""""""""""""""""""""""""""""""
+   * mkfs: fix writing on zoned device when block-group-tree is selected
+   * tune: fix writing on zoned device with option --convert-to-block-group-tree
+   * check:
+      * more progress and error messages
+      * unify handling of unknown command line options with other commands
+   * subvolume delete: remove options --delete-qgroup and --no-delete-qgroup
+     (added in 6.6.3), qgroup deletion does not always work due to delayed
+     background processing of subvolume or set value in
+     sysfs:ggroup/drop_subtree_threshold
+   * other:
+      * misc refactoring
+      * error handling fixes reported by gcc -fanalyzer
+      * documentation updates
+      * new and updated tests
+
 btrfs-progs-6.7 (2024-01-22)
 ----------------------------
    * mkfs: make 4k sectorsize default, recommended minimum kernel for that is