Updates shared attributes to remove old path to fleet docs

[dedemorton]

Fixes attribute that uses old path for Fleet docs. I should have changed this when we changed the path to all versions of the book.

After this PR is merged, we should be able to remove all the old files under https://github.com/elastic/built-docs/tree/master/html/en/ingest-management

[dedemorton]

@elasticmachine run elasticsearch-ci/docs

[dedemorton]

Trying another build because I don't see any reason why the Elasticsearch Guide isn't picking up the changed path.

[gtback]

19:30:43 INFO:build_docs:Bad cross-document links:
19:30:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/elasticsearch/reference/7.10/breaking-changes-7.9.html contains broken links to:
19:30:43 INFO:build_docs:   - en/fleet/7.10/ingest-management-overview.html

@dedemorton This page: https://www.elastic.co/guide/en/elasticsearch/reference/7.10/breaking-changes-7.9.html contains a link to the 7.10 "Elastic Agent" (ingest-management) guide: https://www.elastic.co/guide/en/ingest-management/7.10/ingest-management-overview.html.

It's possible that a full rebuild might fix this, or we might need to update that in the old Elasticsearch docs.

[gtback]

LGTM once the Elasticsearch changes in elastic/elasticsearch#79660 (and backports) land.

[jrodewig]

elastic/elasticsearch#79660 is merged and backported. Rerunning the docs build.

@elasticmachine run elasticsearch-ci/docs