py/runtime: Remove commented-out code from mp_deinit().

These commented-out lines of code have been unused for a long time, so
remove them to avoid confusion as to why they are there.

mp_obj_dict_free() never existed, this line was converted from
mp_map_deinit() and commented out as soon as it was added.  The call to
mp_map_deinit(mp_loaded_modules_map) was commented in
1a1d11fa32.

Fixes issue #3507.

Signed-off-by: Damien George <damien@micropython.org>

py/runtime.c

@@ -155,9 +155,6 @@ void mp_deinit(void) {
     #ifdef MICROPY_PORT_DEINIT_FUNC
     MICROPY_PORT_DEINIT_FUNC;
     #endif
-
-    // mp_obj_dict_free(&dict_main);
-    // mp_map_deinit(&MP_STATE_VM(mp_loaded_modules_map));
 }
 
 mp_obj_t mp_load_name(qstr qst) {