CI error when gadm server is down: add GADM file to datakits

Checklist

• I am using the current main branch or the latest release. Please indicate.
• I am running on an up-to-date pypsa-earth environment. Update via conda env update -f envs/environment.yaml.

Describe the Bug

Please provide a description of what the bug is and add a minimal example/command for reproducing the bug.

With the latest updates, the CI bundles should contain the appropriate gadm data and as such the workflow should not attempt to download them again and trigger the error. This clearly doesn't work and shall be checked.

In particular, there is the need to verify this line: https://github.com/pypsa-meets-earth/pypsa-earth/blob/b205e83c3b631448a778e29257eed551790b9d5c/scripts/build_shapes.py#L100 In the CI case, that condition should be false and so no access to the Davis server should be requested.

@yerbol-akhmetov this is related to what you are experiencing

It should be a quick fix also for new users in case