chore: update authz default config style

apps/emqx_authz/etc/emqx_authz.conf

@@ -1,10 +1,14 @@
 authorization {
-  deny_action: ignore
-  no_match: allow
-  sources: [
+  deny_action = ignore
+  no_match = allow
+  sources =  [
     {
-      type: file
-      path: "{{ platform_etc_dir }}/acl.conf"
+      type = file
+      enable = true
+      # This file is immutable to EMQX.
+      # Once new rules are created from dashboard UI or HTTP API,
+      # the file 'data/authz/acl.conf' is used instead of this one
+      path = "{{ platform_etc_dir }}/acl.conf"
     }
   ]
 }