Reapply allow/deny; fix image tag

Author: sjberman

internal/mode/static/nginx/conf/nginx-plus.conf

@@ -31,6 +31,9 @@ http {
     root /usr/share/nginx/html;
     access_log off;
 
+    allow 127.0.0.1;
+    deny all;
+
     location = /dashboard.html {}
 
     location /api {

site/content/how-to/monitoring/dashboard.md

@@ -24,7 +24,7 @@ To access the dashboard:
 
 The dashboard will look like this:
 
-{{<img src="img/nginx-plus-dashboard.png" alt="NGINX Plus dashboard">}}
+{{<img src="img/nginx-plus-dashboard.png" alt="">}}
 
 
 {{< note >}}The [API](https://nginx.org/en/docs/http/ngx_http_api_module.html), which the dashboard uses to get the metrics, is also accessible using the `/api` path.{{< /note >}}