fix(dashboard): enable dashboard by default

apps/emqx_dashboard/src/emqx_dashboard.erl

@@ -48,16 +48,10 @@ start_listeners() ->
                 'basicAuth' => #{type => http, scheme => basic},
                 'bearerAuth' => #{type => http, scheme => bearer}
             }}},
-    Dispatch =
-        case os:getenv("_EMQX_ENABLE_DASHBOARD") of
-            V when V =:= "true" orelse V =:= "1" ->
-                [{"/", cowboy_static, {priv_file, emqx_dashboard, "www/index.html"}},
-                 {"/static/[...]", cowboy_static, {priv_dir, emqx_dashboard, "www/static"}},
-                 {'_', cowboy_static, {priv_file, emqx_dashboard, "www/index.html"}}
-                ];
-            _ ->
-                []
-        end,
+    Dispatch = [ {"/", cowboy_static, {priv_file, emqx_dashboard, "www/index.html"}}
+               , {"/static/[...]", cowboy_static, {priv_dir, emqx_dashboard, "www/static"}}
+               , {'_', cowboy_static, {priv_file, emqx_dashboard, "www/index.html"}}
+               ],
     BaseMinirest = #{
         base_path => ?BASE_PATH,
         modules => minirest_api:find_api_modules(apps()),