Remove old GPU STS Unpacker.

Beginning of a larger effort to restructure the online unpackers and integrate the new GPU unpacker written by Sebastian Heinemann for his master thesis.

cc @d.smith: Since you're the author, is it ok with you to remove it? I'll add Sebastian's unpacker in the next days. Trying to break down my changes into smaller chunks.

requested review from @d.smith

assigned to @fweig

Fine with me. I'm always in favor of removing outdated/unused filed.

approved this merge request

enabled an automatic merge when the pipeline for 7857af64 succeeds

Dear @d.smith, @fweig, @v.friese, @f.uhlig, @p.-a.loizeau,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

merged

added Online Reconstruction labels