The obsolete firefox plugin was purged in commit 6c53765ac1746ea3cb82554775a37fe43af062e8.
The Signing-Cert certificate (CN=Object Signing,{subject_base}) was used to sign the plugin and has no other use. It should be removed.
master:
Metadata Update from @ftweedal: - Issue assigned to ftweedal - Issue set to the milestone: FreeIPA 4.5