Tweak for swig v4.4

No longer any need to disable heap types for Python < 3.9. See
swig/swig#3219

Author: jim-easterbrook

setup.py

@@ -153,8 +153,6 @@ def get_mod_src_dir(exiv2_version):
 extra_compile_args = []
 define_macros = [('PY_SSIZE_T_CLEAN', None),
                  ('SWIG_TYPE_TABLE', 'exiv2')]
-if sys.version_info < (3, 9):
-    define_macros.append(('SWIG_NO_HEAPTYPES', None))
 if platform in ('linux', 'darwin', 'mingw'):
     extra_compile_args = [
         '-O3', '-Wno-unused-variable', '-Wno-unused-function',