Set up robots.txt or similar to discourage search engines from indexing old spec versions

otherwise people will be searching for "join rules matrix" and not discover restricted rooms, for example.

The issue names no file or test. Start by locating the published specification output and its deployment or configuration entry point, then determine where robots.txt or an equivalent can be served for old versions; done means those versions are discouraged from search indexing.

Written by the indexing model from the issue text.