Just removing a file from a repository with version control does not actually remove it. It is still available in previous commits and remains in the repository, using up space.
Deleting files from all commits of a repository can be required for several reasons:
- Files contain secrets such as passwords or keys
- Files may contain copyrighted, stolen unlicensed data or data not ready for publication
- Large files that should not be in the project making it unnecessarily big and exceed the project space limitations
There is a comprehensive guide
in the GitLab online documentation. Please follow the instructions there.