We duplicated these docs in order to avoid breaking older links, but
this makes it confusing and hard to link to the right copy of the
information. This commit removes the duplication by replacing the docs
at the old locations with stubs that link to the new locations.
* [DOCS] Add 'Troubleshooting an unstable cluster' to nav
* Adjust docs links in code
* Revert "Adjust docs links in code"
This reverts commit f3846b1d78.
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Co-authored-by: David Turner <david.turner@elastic.co>
