Add running settings note in recipe_wenzel16nat.yml documentation

[sloosvel]

Description

This PR adds a note in the recipe documentation to remind to run the recipe setting the output file type to PDF

• Closes Provenance issue in recipe_wenzel16nat.yml with ESMValCore 2.6rc2  #2691
• Link to documentation: https://esmvaltool--2692.org.readthedocs.build/en/2692/recipes/recipe_wenzel16nat.html

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New or updated recipe/diagnostic

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New or updated data reformatting script

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[schlunma]

Looks great, thanks!