py/runtime: Remove comment in mp_import_name about level being 0.

A non-zero level has been supported for some time now.

py/runtime.c

@@ -1319,7 +1319,7 @@ mp_obj_t mp_import_name(qstr name, mp_obj_t fromlist, mp_obj_t level) {
     args[1] = mp_const_none; // TODO should be globals
     args[2] = mp_const_none; // TODO should be locals
     args[3] = fromlist;
-    args[4] = level; // must be 0; we don't yet support other values
+    args[4] = level;
 
     // TODO lookup __import__ and call that instead of going straight to builtin implementation
     return mp_builtin___import__(5, args);