py: Remove MP_STATE_CTX, use MP_STATE_THREAD instead (it's an alias).

MP_STATE_CTX was recently aliased to MP_STATE_THREAD and can now be
removed.
diff --git a/py/runtime.h b/py/runtime.h
index d4b1fa7..1778691 100644
--- a/py/runtime.h
+++ b/py/runtime.h
@@ -83,10 +83,10 @@
 NORETURN void mp_arg_error_terse_mismatch(void);
 NORETURN void mp_arg_error_unimpl_kw(void);
 
-static inline mp_obj_dict_t *mp_locals_get(void) { return MP_STATE_CTX(dict_locals); }
-static inline void mp_locals_set(mp_obj_dict_t *d) { MP_STATE_CTX(dict_locals) = d; }
-static inline mp_obj_dict_t *mp_globals_get(void) { return MP_STATE_CTX(dict_globals); }
-static inline void mp_globals_set(mp_obj_dict_t *d) { MP_STATE_CTX(dict_globals) = d; }
+static inline mp_obj_dict_t *mp_locals_get(void) { return MP_STATE_THREAD(dict_locals); }
+static inline void mp_locals_set(mp_obj_dict_t *d) { MP_STATE_THREAD(dict_locals) = d; }
+static inline mp_obj_dict_t *mp_globals_get(void) { return MP_STATE_THREAD(dict_globals); }
+static inline void mp_globals_set(mp_obj_dict_t *d) { MP_STATE_THREAD(dict_globals) = d; }
 
 mp_obj_t mp_load_name(qstr qst);
 mp_obj_t mp_load_global(qstr qst);