{kokoro} Updating ruby gems at the start of the website job. (#6184)
{kokoro} Updating ruby gems at the start of the website job. (#6184)

We need 3.0.0 for the latest version of bundler, so until kokoro's environment
preinstalls 3.0.0, we need to update.
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