Enable the syncing of dist-git updates back to src-git

[jpopelka]

It's been implemented since #92 but hasn't actually been enabled yet.

From what I remember, I tried it on Fedora and realized, that the DistGitToSourceGitPRHandler.dist_git_local_project (which is run for each commit to any dist-git repo) always clones the dist-git repo even if there's no corresponding source-git repo, which is quite resource-wasteful. So I just stopped the fedsmg pod, all you need to do to enable it is to run the pod again.

For CentOS Stream source-git, a Push events trigger needs to be added to the existing group webhook for Packit in redhat/centos-stream/rpms group settings (you need to find someone with access, try sgallagh).