cachi2: update source containers sources filtration

[MartinBasti]

Cachi2 doesn't provide package but only dependencies.

Cachi2 doesn't use nested directories with dep name, filename must be updated to contain plain name

Maintainers will complete the following section

• [ ] Commit messages are descriptive enough
• [ ] Code coverage from testing does not decrease and new code is covered
• [ ] Python type annotations added to new code
• [ ] JSON/YAML configuration changes are updated in the relevant schema
• [ ] Changes to metadata also update the documentation for the metadata
• [ ] Pull request has a link to an osbs-docs PR for user documentation updates
• [ ] New feature can be disabled from a configuration file