No longer downloading singularity image automatically

[nmerket]

Fixes #256.

Pull Request Description

Instead of fixing the collision I'm just removing the "feature" that would download the singularity image to the run directory. It's better to know and make sure it's in the shared directory in the first place.

Checklist

Not all may apply

• Code changes (must work)
• Tests exercising your feature/bug fix (check coverage report on Checks -> BuildStockBatch Tests -> Artifacts)
• Coverage has increased or at least not decreased. Update minimum_coverage in .github/workflows/ci.yml as necessary.
• All other unit and integration tests passing
• Update validation for project config yaml file changes
• Update existing documentation
• Run a small batch run on Eagle to make sure it all works if you made changes that will affect Eagle
• Add to the changelog_dev.rst file and propose migration text in the pull request

[github-actions]

File	Coverage
All files	84%	✅
base.py	89%	✅
eagle.py	79%	✅
exc.py	57%	✅
local.py	50%	✅
postprocessing.py	84%	✅
utils.py	96%	✅
sampler/base.py	79%	✅
sampler/downselect.py	33%	✅
sampler/precomputed.py	93%	✅
sampler/residential_quota.py	61%	✅
test/test_docker.py	33%	✅
test/test_validation.py	97%	✅
workflow_generator/base.py	90%	✅
workflow_generator/commercial.py	53%	✅
workflow_generator/residential_hpxml.py	83%	✅

Minimum allowed coverage is 33%

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