slapos-node: fix duplicated PYTHON key

This is a fixup of 9a886c4b

component/slapos/obs.cfg

@@ -85,7 +85,6 @@ pre-configure =
   sed -i 's#/opt/slapos/parts/dbus/lib/libdbus-1.la#${dbus:location}/lib/libdbus-1.la#' ${dbus-glib:location}/lib/libdbus-glib-1.la
 environment +=
   LD_LIBRARY_PATH=${dbus:location}/lib
-  PYTHON=${python:location}/bin/python${python:version}
   PYTHON_INCLUDES=-I${python:location}/include/python${python:version}m
   PYTHON_LIBS=-L${python:location}/lib -lpython${python:version}m -lpthread -ldl -lutil -lm
 post-install =