bpo-33375: Fix GCC warning in Python/_warnings.c (GH-7556)

_Py_IDENTIFIER(argv) is now unused.
diff --git a/Python/_warnings.c b/Python/_warnings.c
index 9c7a6e1..d6614b2 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -9,7 +9,6 @@
 MODULE_NAME " provides basic warning filtering support.\n"
 "It is a helper module to speed up interpreter start-up.");
 
-_Py_IDENTIFIER(argv);
 _Py_IDENTIFIER(stderr);
 #ifndef Py_DEBUG
 _Py_IDENTIFIER(default);