fire diagnostic will download some data

[bouweandela]

The fire diagnostic automatically downloads some reference data. This may be a problem on HPC systems without an internet connection. More info: https://docs.esmvaltool.org/en/latest/recipes/recipe_ref_fire.html

[lewisjared]

The guidance for a workaround has been to run ref solve --one-per-diagnostic on a login node first until we have a stronger promise about running without internet.