build: bump required node version (#23439)
build: bump required node version (#23439)

Our current requirement asks for at least Node 12, however the `dev-infra-private` package includes some syntax that is only available in Node 14.

These changes bump the minimum required version to 14.

Fixes #23434.
crisbeto/material2,josephperrott/material2,angular/components,josephperrott/material2,crisbeto/material2,angular/components,josephperrott/material2,crisbeto/material2,josephperrott/material2,angular/components,crisbeto/material2,angular/components,josephperrott/material2