Elasticsearch no longer maintain either of these versions, as per https://www.elastic.co/support/eol

We should remove support for all of these versions from Optimize.

ATs:

• Documentation is updated to no longer include support for Optimize 7.10 & 7.11& 7.12
• We include the deprecation in our upgrade guide
• We no longer run nightly tests against these versions
• We update the client (if necessary)
• (Optional) if our client is one of these versions and uses deprecated methods in the client API, we use the new version of the API