Log Message:
py-packageurl: update to 0.15.6.

0.15.6 (2024-07-25)
-------------------

- Refine support for GitHub /archive/refs/tags/ URLs in ``url2purl``.
  The whole tag is now captured as the version.
  This allows to properly reconstruct valid URLs in ``purl2url``.

0.15.5 (2024-07-24)
-------------------

- Capture the whole git tag as the version for GutHub URL in ``url2purl`` instead of
  adding a version_prefix qualifier.
  Note that the version_prefix qualifier is still supported in ``purl2url`` for
  backward compatibility.
  https://github.com/package-url/packageurl-python/pull/159