[8.17] Update search-across-clusters.asciidoc to reflect the `true` default value of `skip_unavailable` setting. (#120592)#120633

elasticsearchmachine merged 1 commit intoelastic:8.17elastic/elasticsearch:8.17from

astefan:backport/8.17/pr-120592astefan/elasticsearch:backport/8.17/pr-120592Copy head branch name to clipboard