Package intermediates embeds a list of known unexpired, unrevoked intermediate certificates chaining to roots with Websites trust in the Mozilla Root Program.
This dataset is useful to establish connections to misconfigured servers that fail to provide a full certificate chain but provide a valid, publicly trusted end-entity certificate. Some browsers implement similar strategies to successfully establish connections to these sites.
https://pkg.go.dev/filippo.io/intermediates
This is not an official or supported Google product, just some code that happens to be owned by Google.