ci: no longer upload the latest builds on commits
    
    The idea behind this action is to make it possible to compare the
    latest fuzz targets with PRs to figure out whether bugs are really
    reproducible in PRs only. Since forks (including systemd-stable) are
    usually based on the upstream repository where almost all the bugs
    are fixed before releases are cut it should be safe to assume that
    if CFLite finds bugs in PRs they are most likely introduced in those
    PRs.
    
    It should probably be brought back once https://github.com/google/clusterfuzzlite/issues/84
    is fixed.