CI: force cleanup on setup fail

[casperdcl]

Changes

During conda setup, any error will result in a broken environment.
Such broken environments hardcoded in ~/.profile will cause all future jobs to fail.
This PR force-removes environments.

Testing you performed

Related issues/links

• e.g. temperamental conda internal server error (5xx) https://github.com/TomographicImaging/CIL/actions/runs/8551980244/job/23432143727#step:4:332
• follow-up to CI: fix concurrent CUDA runners #1767
• https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell

Checklist

• I have performed a self-review of my code
• I have added docstrings in line with the guidance in the developer guide
• I have updated the relevant documentation
• I have implemented unit tests that cover any new or modified functionality
• CHANGELOG.md has been updated with any functionality change
• Request review from all relevant developers
• Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
• I confirm that the contribution does not violate any intellectual property rights of third parties