bpo-42208: Fix test_gdb for gc_collect_main() name (GH-23041)

The gcmodule.c collect() function was renamed to gc_collect_main():
update gdb/libpython.py (python-gdb.py).

Tools/gdb/libpython.py

@@ -1605,8 +1605,8 @@ class Frame(object):
             return (name == 'take_gil')
 
     def is_gc_collect(self):
-        '''Is this frame "collect" within the garbage-collector?'''
-        return self._gdbframe.name() == 'collect'
+        '''Is this frame gc_collect_main() within the garbage-collector?'''
+        return self._gdbframe.name() in ('collect', 'gc_collect_main')
 
     def get_pyop(self):
         try: