nixguix: Update heuristic checking if URL targets a tarball file

In addition to query parameters also check if any part of URL path contains a tarball filename.

It fixes the detection of some tarball URLs provided in Guix manifest like https://bordeaux.guix.gnu.org/file/abduco-0.6.tar.gz/sha256/1x1m58ckwsprljgmdy93mvgjyg9x3cqrzdf3mysp0mx97zhhj2f9.

Related to swh/meta#3781 (closed).