Change Filebeat template IP variable name

[nmkoremblum]

Wazuh version	Install type	Action performed	Platform
4.3	Manager	Install	Linux

Currently, on the filebeat.yml configuration file, we have the elasticsearch_ip "variable" to be replaced with an indexer's IP.

I think it would be good to change such variable name to a more generic one such as "indexer_ip" or "wazuh_indexer_ip" which goes in concordance with our offering.

Best Regards,

Mariano Koremblum