chore(emqx_authz): fix `rule()` type example

Use `action()` type which is a correct and defined type.

apps/emqx_authz/etc/acl.conf

@@ -20,7 +20,7 @@
 %%
 %% -type(permission() :: allow | deny).
 %%
-%% -type(rule() :: {permission(), who(), access(), topics()} | {permission(), all}).
+%% -type(rule() :: {permission(), who(), action(), topics()} | {permission(), all}).
 %%--------------------------------------------------------------------
 
 {allow, {username, {re, "^dashboard$"}}, subscribe, ["$SYS/#"]}.