chore(acl): fully match `dashboard` username

Co-authored-by: Ilya Averyanov <av@rubybox.dev>

apps/emqx_authz/etc/acl.conf

@@ -23,7 +23,7 @@
 %% -type(rule() :: {permission(), who(), access(), topics()} | {permission(), all}).
 %%--------------------------------------------------------------------
 
-{allow, {username, {re, "^dashboard?"}}, subscribe, ["$SYS/#"]}.
+{allow, {username, {re, "^dashboard$"}}, subscribe, ["$SYS/#"]}.
 
 {allow, {ipaddr, "127.0.0.1"}, all, ["$SYS/#", "#"]}.
 

changes/ce/fix-10172.en.md

@@ -1,9 +1,9 @@
 Fix the incorrect default ACL rule, which was:
 ```
-{allow, {username, "^dashboard?"}, subscribe, ["$SYS/#"]}.
+{allow, {username, "^dashboard$"}, subscribe, ["$SYS/#"]}.
 ```
 
-However, it should use `{re, "^dashboard?"}` to perform a regular expression match:
+However, it should use `{re, "^dashboard$"}` to perform a regular expression match:
 ```
 {allow, {username, {re,"^dashboard?"}}, subscribe ,["$SYS/#"]}.
 ```

changes/ce/fix-10172.zh.md

@@ -1,6 +1,6 @@
 修复错误的默认 ACL 规则，之前是：
 ```
-{allow, {username, "^dashboard?"}, subscribe, ["$SYS/#"]}.
+{allow, {username, "^dashboard$"}, subscribe, ["$SYS/#"]}.
 ```
 但执行正则表达式的匹配应该使用 `{re, "^dashboard?”}`：
 ```