memblock tests: remove completed TODO item

Remove completed item from TODO list.
Signed-off-by: Rebecca Mckeever <remckee0@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>

tools/testing/memblock/TODO

@@ -23,6 +23,3 @@ TODO
 
 5. Add tests for memblock_alloc_node() to check if the correct NUMA node is set
    for the new region
-
-6. Update comments in tests/basic_api.c to match the style used in
-   tests/alloc_*.c