Doc: Fix templating error in integration plugin header (elastic#13324)

Author: karenzone

docs/include/plugin_header-integration.asciidoc

@@ -34,6 +34,6 @@ endif::[]
 ==== Getting Help
 
 For questions about the plugin, open a topic in the http://discuss.elastic.co[Discuss] forums. 
-For bugs or feature requests, open an issue in https://github.com/logstash-plugins/logstash-integration-{plugin}[Github].
+For bugs or feature requests, open an issue in https://github.com/logstash-plugins/logstash-integration-{integration}[Github].
 For the list of Elastic supported plugins, please consult the https://www.elastic.co/support/matrix#matrix_logstash_plugins[Elastic Support Matrix].