Do not try to override the value of the PYTHON variable with non-existing PYTHON3 one (#383)

Fixes: #382

Author: bigon

bindings/swig/python3/Makefile.am

@@ -26,7 +26,6 @@ AM_CPPFLAGS = -I. -I$(top_builddir) -I${top_srcdir}/lib $(PYTHON3_INCLUDES)
 LIBS = $(top_builddir)/lib/libaudit.la
 SWIG_FLAGS = -python
 SWIG_INCLUDES = -I. -I$(top_builddir) -I${top_srcdir}/lib $(PYTHON3_INCLUDES)
-PYTHON = $(PYTHON3)
 pyexec_PYTHON = audit.py
 pyexec_LTLIBRARIES = _audit.la
 pyexec_SOLIBRARIES = _audit.so