Fix usage notebook

[aulemahal]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes Usage Notebook in Docs seems to be broken #946
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• HISTORY.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.
• bumpversion patch has been called on this branch
• The relevant author information has been added to .zenodo.json

What kind of change does this PR introduce?

• I added an example in Indexing within indicators #934 that modified the variable used further down. This PR switches the added example with the one generating the good data.

Does this PR introduce a breaking change?

No

Other information:

[review-notebook-app]

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[coveralls]

Coverage remained the same at 90.721% when pulling d35c006 on fix-946 into 2fc7dd8 on master.