Remove `-shared` from Windows release artifacts

[indygreg]

Windows static builds were removed in #234.

We preserved the -shared target triple suffix for the moment. But it is no longer needed, as its sole role was to disambiguate the static and shared Windows builds. Since there is now only a single variant, no such label is needed.

If we remove the -shared suffix, there will be consumers who will need to update code to point to the new value. We may want to consider double publishing the -shared and sans--shared release artifacts during a transition period to avoid forced breakage. The download stats can be used to determine when it is safe to stop publishing the -shared artifacts.

[charliermarsh]

I can take this follow-up.