refactor(material/snack-bar): use classList.toggle
refactor(material/snack-bar): use classList.toggle

With Angular dropping IE11 support in version 13, we can now use `classList.toggle` with the second `force` param. Related to #7374

crisbeto/material2,crisbeto/material2,angular/components,crisbeto/material2,angular/components,angular/components,josephperrott/material2,josephperrott/material2,angular/components,josephperrott/material2,josephperrott/material2,josephperrott/material2,crisbeto/material2