Migrate `mdprep` to the `CCPBioSim` organisation

[harryswift01]

Description

The mdprep GitHub Actions workflows are currently hanging during the test stage for the mdprep package. Minor updates are required in the workflow file (mdprep/.github/workflows/python-app.yml) to ensure the tests run correctly.

Additionally, the repository’s configuration and documentation should be updated to reflect the migration from the hecbiosim organisation to the CCPBioSim organisation, including clone URLs and any organisation references.

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Tasks

• Update mdprep/.github/workflows/python-app.yml so that tests complete successfully
• Verify that all CI jobs pass on all supported platforms
• Update clone URLs and repository references from hecbiosim → CCPBioSim
• Confirm that GitHub Pages or documentation links point to the new organisation