change snackbar to default to use the new snackbar and not legacy (#5732)
change snackbar to default to use the new snackbar and not legacy (#5732)

We are now officially moving to use the new Snackbar by default.

This is the last step for the internal bug seen here: b/116850150

### **This is a breaking change.**

material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios