Remove python2 leftovers

[trufae]

root@c0606c7eae3e:/capstone/bindings/python# make install
rm -rf src/
if test -n ""; then \
	python2 setup.py build install --root=""; \
else \
	python2 setup.py build install; \
fi
/bin/sh: 4: python2: not found
make: *** [Makefile:11: install] Error 127

git grep

root@c0606c7eae3e:/capstone/bindings/python# git grep python2
Makefile:PYTHON2 ?= python2
capstone/__init__.py:_python2 = sys.version_info[0] < 3
capstone/__init__.py:if _python2:
capstone/__init__.py:    if _python2:
capstone/__init__.py:        '''if not _python2:

actually doing make PYTHON2=python3 works just fine. so i dont see the point on keep supporting a 12 year old version and deprecated interpreter