Don't update bundler gem
Don't update bundler gem

There are currently issues with certain upstream version combinations:

  https://github.com/bundler/bundler/issues/6144
  https://github.com/rubygems/rubygems/issues/2055

So don't do a manual update of the bundler gem until they are resolved
so we can continue to run travis builds in the meantime.

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