lib: fix calloc warning on recent compiler

lib: fix calloc warning on recent compiler

Fix the following compiler warning:
```
lib/elf_py.c: In function _elffile_load_:
lib/elf_py.c:1310:34: warning: _calloc_ sizes specified with _sizeof_ in the earlier argument and not in the later argument [-Wcalloc-transposed-args]
 1310 |         w->sects = calloc(sizeof(PyObject *), w->ehdr->e_shnum);
      |                                  ^~~~~~~~
lib/elf_py.c:1310:34: note: earlier argument should specify number of elements, later size of each element
```

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>