klibc: malloc.h: fix incorrect comment

At some point, I expected to use the block size to also encode the
block pointer.  This turns out to be fairly messy when dealing with
sparse allocations (as one would get from using mmap() to
allocate memory) as it would require putting a header on all holes,
which gets ugly quick.

Thus remove the incorrect comment.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
1 file changed