btrfs: send: cleanup unneeded return variable in changed_verity()

As all changed_* functions need to return something, just return 0
directly here, as the verity status is passed via the context.

Reported by LKP: fs/btrfs/send.c:6877:5-8: Unneeded variable: "ret". Return "0" on line 6883

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202410092305.WbyqspH8-lkp@intel.com/


Signed-off-by: Christian Heusel <christian@heusel.eu>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>