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 google/clusterfuzzlite#84
is fixed.