[sorno_top_size_files] Fix the last item shown in top files, which is not in the list of top files

Summary:
Fix the last item shown in top files, which is not in the list of top files.
The bug comes from the fact that heapq.heapreplace removes an item before
adding an item, so there is always at least one item in the heap which is not
in the top files if heaprepplace is used. This is fixed by setting the heap
size to be the given num + 1, then take out that extra item before printing
out the top files list.