chore(script): update_appup.escript support the update cmd

We often use the advanced directive `update` when hot upgrading
gen_server, gen_statem, and other such processes, and it will be
parsed as:
```
{suspend,[Mod]},
{load,{Mod,brutal_purge,brutal_purge}},
{code_change,up,[{Mod,[Extra]}]},
{resume,[Mod]},
```
So, we should treat the update instruction as having completed the
upgrade of this module.

scripts/update_appup.escript

@@ -324,6 +324,8 @@ process_old_action({add_module, Module}) ->
     [Module];
 process_old_action({delete_module, Module}) ->
     [Module];
+process_old_action({update, Module, _Change}) ->
+    [Module];
 process_old_action(LoadModule) when is_tuple(LoadModule) andalso
                                     element(1, LoadModule) =:= load_module ->
     element(2, LoadModule);