Update screenshot and instructions

The field labels for enabling Fluentd changed; this MR updates the
screenshot and text instructions to match the UI.

doc/user/clusters/applications.md

@@ -537,12 +537,12 @@ To enable Fluentd:
 1. Navigate to **{cloud-gear}** **Operations > Kubernetes** and click
    **Applications**. You will be prompted to enter a host, port and protocol
    where the WAF logs will be sent to via syslog.
-1. Provide the host domain name or URL in **SIEM URL or Host**.
+1. Provide the host domain name or URL in **SIEM Hostname**.
 1. Provide the host port number in **SIEM Port**.
 1. Select a **SIEM Protocol**.
 1. Check **Send ModSecurity Logs**. If you do not select this checkbox, the **Install**
    button is disabled.
-1. Click **Install**.
+1. Click **Save changes**.
 
 ![Fluentd input fields](img/fluentd_v12_10.png)