Correctly disable the cache in development
Correctly disable the cache in development

Setting a cache_ttl only has an effect on responses that don't include an
Expires header. Content API now issues Expires headers, so this configuration
wasn't doing what it was intended to do.

Now that we have a semantic way of saying "no caching please", let's just use
that.

alphagov/frontend,alphagov/frontend,alphagov/frontend,alphagov/frontend