btrfs: check-integrity: remove unnecessary failure messages during memory allocation

As there is a dump_stack() done on memory allocation failures, these
messages might as well be deleted instead.

Signed-off-by: Liao Pingfang <liao.pingfang@zte.com.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor tweaks ]
Signed-off-by: David Sterba <dsterba@suse.com>