Update tls-encryption.asciidoc (#17387) (#17444)

The referenced elasticsearch output plugin has deprecated the options that were specified (`ssl`, `cacert`) https://www.elastic.co/guide/en/logstash/current/plugins-outputs-elasticsearch.html#plugins-outputs-elasticsearch-deprecated-options

When I tried using the `ssl` option I noticed a warning in the logstash logs:
```
[WARN ][logstash.outputs.elasticsearch] You are using a deprecated config setting "ssl" set in elasticsearch. Deprecated settings will continue to work, but are scheduled for removal from logstash in the future. Set 'ssl_enabled' instead. If you have any questions about this, please visit the #logstash channel on freenode irc.
```

I have updated this document with the suggested new options to use instead.

(cherry picked from commit 3402310)

Co-authored-by: Matt Johnson <[email protected]>

Author: mergify[bot]

Diff for: docs/static/security/tls-encryption.asciidoc

@@ -3,21 +3,23 @@
 === Configuring Logstash to use TLS/SSL encryption
 
 If TLS encryption is enabled on an on premise {es} cluster, you need to
-configure the `ssl` and `cacert` options in your Logstash `.conf` file:
+configure the `ssl_enabled` and `ssl_certificate_authorities` options in your Logstash `.conf` file:
+
+NOTE: See https://www.elastic.co/guide/en/logstash/current/plugins-outputs-elasticsearch.html[elasticsearch output plugin documentation] for a full list of options
 
 [source,js]
 --------------------------------------------------
 output {
   elasticsearch {
     ...
-    ssl => true
-    cacert => '/path/to/cert.pem' <1>
+    ssl_enabled => true
+    ssl_certificate_authorities => '/path/to/cert.pem' <1>
   }
 }
 --------------------------------------------------
 <1> The path to the local `.pem` file that contains the Certificate
     Authority's certificate.
-    
+
 NOTE: Hosted {ess} simplifies security. This configuration step is not necessary for hosted Elasticsearch Service on Elastic Cloud.
 {ess-leadin-short} 
-    
+