Remove unnecessary conversion in get_supported
Remove unnecessary conversion in get_supported

Now that we're fully using packaging.tags, everything in the supported
list is already Tag.

Further, since each function is responsible for its own set of
non-overlapping tags, we can also remove the de-duplication.

xavfernandez/pip,xavfernandez/pip,sbidoul/pip,sbidoul/pip,pypa/pip,pfmoore/pip,pradyunsg/pip,pfmoore/pip,xavfernandez/pip,pradyunsg/pip,pypa/pip