Change ECE current docs version

[lcawl]

This PR updates the "current" branch for the Elastic Cloud Enterprise docs in the conf.yaml

The PR currently fails due to:

INFO:build_docs:Bad cross-document links:
--
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud-enterprise/3.7/ece-migrate-ccs.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-other-ece.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud-enterprise/3.7/ece-remote-cluster-other-ece.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-ece-ess.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud-enterprise/3.7/ece-remote-cluster-same-ece.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-same-ece.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud/current/ec-enable-ccs.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-ece-ess.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud/current/ec-remote-cluster-ece.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-ece-ess.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud/latest/ec-enable-ccs.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-ece-ess.html
  | INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/cloud/latest/ec-remote-cluster-ece.html contains broken links to:
  | INFO:build_docs:   - en/cloud-enterprise/current/ece-remote-cluster-ece-ess.html
  | 🚨 Error: The command exited with status 255

I am testing whether we can fix that problem by making the ece-ref attribute version-aware in #2997

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[kilfoyle]

@lcawl Just in case it helps, it seems that some (but not all) of those broken links (the remote-cluster-ece-ess ones) should be fixable by reverting this revert PR: https://github.com/elastic/cloud/pull/126396

[lcawl]

This PR has been replaced by #2999