DOC: update wheel DL docs
DOC: update wheel DL docs

* update our release workflow documentation to reflect
usage of `tools/download-wheels.py` instead of the previous
usage of `terryfy`/`wheel-uploader` for pulling down the
staged release wheels

* the new tool requires `1/3` the number of incantations, downloads
the assets more quickly, and requires less explanation/documentation

Eric89GXL/scipy,matthew-brett/scipy,pizzathief/scipy,scipy/scipy,perimosocordiae/scipy,vigna/scipy,anntzer/scipy,e-q/scipy,vigna/scipy,perimosocordiae/scipy,vigna/scipy,nmayorov/scipy,rgommers/scipy,pizzathief/scipy,scipy/scipy,endolith/scipy,rgommers/scipy,ilayn/scipy,anntzer/scipy,perimosocordiae/scipy,tylerjereddy/scipy,Eric89GXL/scipy,e-q/scipy,endolith/scipy,anntzer/scipy,scipy/scipy,WarrenWeckesser/scipy,matthew-brett/scipy,WarrenWeckesser/scipy,vigna/scipy,nmayorov/scipy,endolith/scipy,Stefan-Endres/scipy,andyfaff/scipy,mdhaber/scipy,zerothi/scipy,andyfaff/scipy,ilayn/scipy,matthew-brett/scipy,anntzer/scipy,nmayorov/scipy,zerothi/scipy,grlee77/scipy,andyfaff/scipy,grlee77/scipy,Stefan-Endres/scipy,pizzathief/scipy,Stefan-Endres/scipy,nmayorov/scipy,tylerjereddy/scipy,endolith/scipy,zerothi/scipy,mdhaber/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,tylerjereddy/scipy,endolith/scipy,WarrenWeckesser/scipy,scipy/scipy,endolith/scipy,grlee77/scipy,Eric89GXL/scipy,matthew-brett/scipy,e-q/scipy,mdhaber/scipy,rgommers/scipy,WarrenWeckesser/scipy,scipy/scipy,WarrenWeckesser/scipy,perimosocordiae/scipy,perimosocordiae/scipy,ilayn/scipy,tylerjereddy/scipy,ilayn/scipy,zerothi/scipy,andyfaff/scipy,anntzer/scipy,nmayorov/scipy,e-q/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,mdhaber/scipy,pizzathief/scipy,grlee77/scipy,mdhaber/scipy,andyfaff/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,scipy/scipy,rgommers/scipy,grlee77/scipy,ilayn/scipy,rgommers/scipy,Eric89GXL/scipy,tylerjereddy/scipy,perimosocordiae/scipy,pizzathief/scipy,ilayn/scipy,andyfaff/scipy,mdhaber/scipy,anntzer/scipy,e-q/scipy,zerothi/scipy,matthew-brett/scipy,vigna/scipy,zerothi/scipy