build: change alpha/beta prerelease options to "next" (#17285)
build: change alpha/beta prerelease options to "next" (#17285)

Angular no longer marks releases as "alpha" or "beta", instead using "next".
crisbeto/material2,DevVersion/material2,andrewseguin/material2,mmalerba/material2,mmalerba/material2,DevVersion/material2,josephperrott/material2,crisbeto/material2,DevVersion/material2,josephperrott/material2,Jefiozie/material2,angular/components,DevVersion/material2,andrewseguin/material2,Jefiozie/material2,andrewseguin/material2,Jefiozie/material2,angular/components,josephperrott/material2,DevVersion/material2,crisbeto/material2,mmalerba/material2,andrewseguin/material2,crisbeto/material2,angular/components,andrewseguin/material2,Jefiozie/material2,josephperrott/material2,josephperrott/material2,angular/components,mmalerba/material2,Jefiozie/material2,mmalerba/material2