package/python: re-enable hashlib

package/python: re-enable hashlib

In commit e5cfb319f9493d677f059ca72b80f7fa22fc9f0f,
the committer did add the flag `--disable-hashlib` to python,
even though this was not part of the original patch
(https://patchwork.ozlabs.org/patch/1231905/).

This unexpected modification break the builds of waf-based
packages, such as jack2, mpv or aubio. This commit therefore

Fixes: http://autobuild.buildroot.net/results/2b3/2b377bcfda6e7ae4d6bb894664e3a4cb13a70b6d/
Fixes: http://autobuild.buildroot.net/results/cd5/cd5da8cb3da8479ebee60d011ce0c5dc0e59aab7/
Signed-off-by: Titouan Christophe <titouan.christophe@railnova.eu>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>