DOC: clarify the meaning of whitening for cluster.vq.whiten()
DOC: clarify the meaning of whitening for cluster.vq.whiten()

Closes gh-12446

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