build: Remove python 2 build
Python 2 is EOL since Jan 2020, but we kept the option to build for
python2. Remove this option so we can remove the python 2 hacks from the
sanlock C extension module.
Users that want python 2 support should use sanlock <= 3.8.2.
Signed-off-by: Nir Soffer <nsoffer@redhat.com>