docs(select): hide private api from docs (#17837)
docs(select): hide private api from docs (#17837)

Hides the `MatSelect.overlayDir` from the docs since it's supposed to be a private API. Also marks it to be renamed in 10.0.0.

Fixes #17678.
mmalerba/material2,angular/components,Jefiozie/material2,andrewseguin/material2,josephperrott/material2,andrewseguin/material2,mmalerba/material2,andrewseguin/material2,Jefiozie/material2,mmalerba/material2,crisbeto/material2,crisbeto/material2,DevVersion/material2,angular/components,angular/components,josephperrott/material2,josephperrott/material2,crisbeto/material2,Jefiozie/material2,DevVersion/material2,angular/components,mmalerba/material2,DevVersion/material2,Jefiozie/material2,andrewseguin/material2,andrewseguin/material2,mmalerba/material2,josephperrott/material2,crisbeto/material2,DevVersion/material2,Jefiozie/material2,josephperrott/material2,DevVersion/material2