btrfs: only print error message when checking item size in print_extent_item()

The extent item used to have a v0 that was removed in 6.6. There's a
check for minimum expected size that could lead to
btrfs_handle_fs_error() that would make the filesystem read-only. As we
don't have v0 anymore (and haven't seen any reports in the deprecation
period), handle this in a less intrusive way.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>