Mark asset_bom_removal-rails as retired
Mark asset_bom_removal-rails as retired

It is [no longer used anywhere](https://github.com/search?q=org%3Aalphagov+asset_bom_removal-rails+-repo%3Aalphagov%2Fasset_bom_removal-rails+-repo%3Aalphagov%2Fgovuk-dependency-analysis&type=code).
alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs