Update maturity level for Cognite connector

[evertoncolling]

This PR updates existing documentation for the two Power Query connectors developed and maintained by Cognite, mainly focusing on the update on maturity level for the REST API connector.

[learn-build-service-prod]

Learn Build status updates of commit b38573a:

✅ Validation status: passed

File	Status	Preview URL	Details
powerquery-docs/connectors/cognite-data-fusion-(odata).md	✅Succeeded
powerquery-docs/connectors/cognite-data-fusion-(rest-api).md	✅Succeeded
powerquery-docs/connectors/index.md	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-odata/get-data-dialog.png	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-odata/online-get-data.png	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-rest/get-data-dialog.png	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-rest/online-connection-credentials.png	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-rest/online-connection-settings.png	✅Succeeded
powerquery-docs/connectors/media/cognite-data-fusion-rest/online-get-data.png	✅Succeeded
powerquery-docs/toc.yml	✅Succeeded

For more details, please refer to the build report.

[prmerger-automator]

PRMerger Results

Issue	Description
Yaml File(s)	This PR includes changes to .yml file(s) owned by another author.
Image File	This PR added or updated an image file(s).
Index File	This PR contains a change to the index file.

[v-dirichards]

@DougKlopfenstein

Can you review the proposed changes?

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team