software/pureftpd: Updates software release to be python3 compliant
- Updates component/pureftpd url to 1.0.49 version because the one provided do not exist anymore (the 1.0.46 version exists now under the path https://download.pureftpd.org/pub/pure-ftpd/releases/obsolete/pure-ftpd-1.0.46.tar.bz2)
- Deletes explicit slapos.toolbox dependency because it's automatically installed by monitor stack