{.kokoro} Pin the website job's node version to v8. (#6472)
{.kokoro} Pin the website job's node version to v8. (#6472)

The docsite-generator relies on node v8 to build and validate the website. Node has since released multiple major versions that have introduced incompatibilities with the docsite-generator. There are two ways to address this:

1. Update docsite-generator to support the latest node.
2. Pin the node version to the last docsite-generator-supported version of node.

Given that docsite-generator is in maintenance mode and unlikely to be updated, this PR implements option 2 in order to fix our website job.
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