Changes:
* Removes several `[testenv="gold+"]` attributes from the docs. `gold+` is not a valid [subscription level](https://www.elastic.co/subscriptions) or testenv value.
* Moves two `[testenv="basic"]` attributes to the file header. This makes the `testenv` placement consistent and fixes the yml file generated from `docs/reference/snapshot-restore/register-repository.asciidoc`.
Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>
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