py/runtime: Remove obsolete comment about mp_parse_compile_execute.

mp_locals_get/set and mp_globals_get/set are now static-inline functions so
this comment is no longer correct.

py/runtime.c

@@ -1421,7 +1421,6 @@ void mp_import_all(mp_obj_t module) {
 
 #if MICROPY_ENABLE_COMPILER
 
-// this is implemented in this file so it can optimise access to locals/globals
 mp_obj_t mp_parse_compile_execute(mp_lexer_t *lex, mp_parse_input_kind_t parse_input_kind, mp_obj_dict_t *globals, mp_obj_dict_t *locals) {
     // save context
     mp_obj_dict_t *volatile old_globals = mp_globals_get();