Remove dsingleton/deploy-lag-radiator from dashboard.yml
Remove dsingleton/deploy-lag-radiator from dashboard.yml

This is the only non-alphagov repository referenced in our configs.
It doesn't appear anywhere in the compiled Dev Docs apart from the
bottom of the homepage, under
https://docs.publishing.service.gov.uk/#misc.

I don't see any value in keeping it, and it's currently breaking
the build and preventing us from simplifying the code.

Trello: https://trello.com/c/of45ytdG/182-reduce-unnecessary-github-api-requests

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs