Add a zenodo link to natura.tiff

[ekatef]

Changes proposed in this Pull Request

Adds zenodo link to natura.tiff source file to keep bundle config consistent, as all other urls normally provide two sources.

Note that the zenodo link to natura.tiff has been previously erroneously placed under the cutout for North America which has been fixed by #1055.

Checklist

• I consent to the release of this PR's code under the AGPLv3 license and non-code contributions under CC0-1.0 and CC-BY-4.0.
• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Newly introduced dependencies are added to envs/environment.yaml and doc/requirements.txt.
• Changes in configuration options are added in all of config.default.yaml and config.tutorial.yaml.
• Add a test config or line additions to test/ (note tests are changing the config.tutorial.yaml)
• Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[davide-f]

Feel free to merge as CI passes :D great catch!

[davide-f]

Merging :D