golang scans fail with x509 TLS errors

[sblatnick]

Every time we scan a Go repo using dependabot/cli, we get many failures with:

proxy | 2024/08/06 17:45:57 [374] GET [https://golang.org:443/x/tools?go-get=1](https://golang.org/x/tools?go-get=1)
  proxy | 2024/08/06 17:45:57 [118] WARN: Cannot read TLS response from mitm'd server tls: failed to verify certificate: x509: certificate signed by unknown authority

This is running in a docker-in-docker image running in our network as part of a Jenkins job. I can't reproduce this issue in the same image locally.