Aside from one minor textual nit (that wasn't introduced by this PR, but on a line touched by it), I checked over the importlib* docs and there indeed doesn't appear to be remaining references to unsupported versions, so LGTM.

One note, though—will only changes referring to Python versions that were unsupported at the time the backport target was released be backported? It seems a little odd to actively remove docs content that refers to versions supported at the time an older bugfix version just because an EoL date was later reached, as well as extra work.

It would seem to make more sense to have a consistent policy of just mentioning the Python versions supported as of the release of the target version, rather than going through and updating all the bugfix, pre-release and future docs at the moment an older version goes EoL, since otherwise up to 4 sets of docs need to be updated with every EoL on a rigid schedule, as opposed to just one set per release at any point between branching the previous release and the current release.