[DOCS] Add missing setting skip_unavailable to example
[DOCS] Add missing setting skip_unavailable to example

The example to delete a remote cluster is missing the `skip_unavailable` setting which results in an error:
```
        "type": "illegal_argument_exception",
        "reason": "missing required setting [cluster.remote.tiny-test.seeds] for setting [cluster.remote.tiny-test.skip_unavailable]"
```
gingerwizard/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,gingerwizard/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,nknize/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch