Update Elasticsearch docs to use 8.19 branch for 8.x

[colleenmcginnis]

Related to #3206, #3207, #3208

Updates Elasticsearch docs to use 8.19 branch for 8.x.

Here are the repos that have been changed:

Repo	Branch
elastic/apm-server	8.19
elastic/beats	8.19
elastic/cloud-assets	8.19
elastic/curator	8.x
elastic/ecs	8.x
elastic/eland	8.x
elastic/elasticsearch-hadoop	8.19
elastic/elasticsearch-java	8.x
elastic/elasticsearch-js	8.x
elastic/elasticsearch-ruby	8.x
elastic/elasticsearch-net	8.x
elastic/elasticsearch-php	8.x
elastic/elasticsearch-py	8.x
elastic/elasticsearch-perl	8.x
elastic/go-elasticsearch	8.x
elastic/elasticsearch-rs	8.x
elastic/elasticsearch	8.19
elastic/enterprise-search-pubs	8.x
elastic/enterprise-search-js	8.x
elastic/enterprise-search-php	8.x
elastic/enterprise-search-python	8.x
elastic/enterprise-search-ruby	8.x
elastic/ingest-docs	8.x
elastic/kibana	8.19
elastic/logstash	8.19
elastic/logstash-docs	8.19
elastic/observability-docs	8.x
elastic/security-docs	8.x
elastic/stack-docs	8.x
elastic/tech-content	8.x

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[lcawl]

LGTM