ITL docs: Replace unmaintained anchor/nagios-plugin-elasticsearch

[martialblog]

Replaced with the currently maintained NETWAYS/check_elasticsearch.

Fixes #6798

[julianbrost]

That looks like an entirely new and incompatible plugin. Can you make an argument why it should completely replace the existing one? Like is that one so broken/outdated/whatever by now that it's unlikely that anyone is still using it (see also #6798 (comment))?

[martialblog]

One argument could be that anchor/nagios-plugin-elasticsearch only works with Python2 and is unmaintained, so there is likely no Python3 version on the horizon.

python3 --version          
Python 3.12.3

python3 check_elasticsearch 
  File "/tmp/nagios-plugin-elasticsearch/check_elasticsearch", line 169
    except KeyError, e:

Another could be that anchor/nagios-plugin-elasticsearch does not work on recent Elasticsearch versions:

podman run --name es8 -p 9200:9200 -m 1g --rm -it -e "xpack.security.enabled=false" -e "discovery.type=single-node" docker.elastic.co/elasticsearch/elasticsearch:8.18.4

python --version
Python 2.7.18

python check_elasticsearch -H localhost -p 9200
API failure

I understand that removal is a drastic measure. Is there a deprecation path for ITL entries?