Remove the code that (un)installed the gds-nagios-plugins package
Remove the code that (un)installed the gds-nagios-plugins package

- Now that Puppet has run everywhere with the changes from 43e4afebe -
  to uninstall the `gds-nagios-plugins` package - we can remove the
  `exec` that did that.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet