[pygobject] Don't call PyEval_InitThreads() with Python 3.9+

[Christoph Reiter <creiter src gnome org>]

commit 2913e72d85269d6b307dc054946a88cbba6707de
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Tue Oct 6 11:29:56 2020 +0200

    Don't call PyEval_InitThreads() with Python 3.9+
    
    The GIL is now created by Python at initialization time no matter what.
    PyEval_InitThreads() triggers a deprecation warning and will be removed in
    3.10 so don't use it with 3.9+.

 gi/gimodule.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/gi/gimodule.c b/gi/gimodule.c
index 890a6bfa..0901e738 100644
--- a/gi/gimodule.c
+++ b/gi/gimodule.c
@@ -2522,12 +2522,16 @@ PYGI_MODINIT_FUNC PyInit__gi(void) {
     module = PyModule_Create(&__gimodule);
     PyObject *module_dict = PyModule_GetDict (module);
 
+#if PY_VERSION_HEX < 0x03090000
+    /* Deprecated since 3.9 */
+
     /* Always enable Python threads since we cannot predict which GI repositories
      * might accept Python callbacks run within non-Python threads or might trigger
      * toggle ref notifications.
      * See: https://bugzilla.gnome.org/show_bug.cgi?id=709223
      */
     PyEval_InitThreads ();
+#endif
 
     PyModule_AddStringConstant(module, "__package__", "gi._gi");