reverts the changes from ec64eebfd6
it brakes some of the flake process we use,
setting 'allow-import-from-derivation' doesn't seem like a good fix to me and doesn't work in all cases.
I couldn't find any other solution to fix it for now,
so we will revert it for now, until we have a better solution.
Do this to be in line with other places, where resources get fetched
using git and to hopefully avoid errors such as:
Cannot find Git revision 'da9d3ead9d97ce0fef7538638326264957e2f1b4' in ref 'trunk' of repository 'ssh://forgejo@git.hamburg.ccc.de/CCCHH/infrastructure-authorized-keys.git'! Please make sure that the rev exists on the ref you've specified or add allRefs = true; to fetchGit.
This issue was discovered while trying to make the new hydra work.
