stm32/mpconfigport.h: Remove unused root pointer for BTstack bindings.
This was a cut-and-paste error from the NimBLE bindings.
@@ -271,7 +271,7 @@ struct _mp_bluetooth_nimble_root_pointers_t;
#if MICROPY_BLUETOOTH_BTSTACK
struct _mp_bluetooth_btstack_root_pointers_t;
-#define MICROPY_PORT_ROOT_POINTER_BLUETOOTH_BTSTACK void **bluetooth_nimble_memory; struct _mp_bluetooth_btstack_root_pointers_t *bluetooth_btstack_root_pointers;
+#define MICROPY_PORT_ROOT_POINTER_BLUETOOTH_BTSTACK struct _mp_bluetooth_btstack_root_pointers_t *bluetooth_btstack_root_pointers;
#else
#define MICROPY_PORT_ROOT_POINTER_BLUETOOTH_BTSTACK
#endif
