Revert "package/cracklib: add python3 support"

This reverts commit f5845954.
It in fact depends on a previous patch to python that was not applied
[0], as upstream believes it is dangerous [1], and is still debating the
proper solution [2].

[0] https://patchwork.ozlabs.org/project/buildroot/patch/20200202205306.1785085-1-fontaine.fabrice@gmail.com/
[1] https://bugs.python.org/issue39026#msg369309
[2] https://bugs.python.org/issue39026



Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>