Ct iteration

Suppose to be 16px.
I think I did that because the alert-flag [sets the font-size](https://github.com/LandRegistry/style-guide/blob/e34738c9d7b4c5b2a876166dafb66480d184fceb/app/static/development/landregistry-elements/_tags.scss#L27) but I wanted it a touch smaller.
I suppose I could use `@include core-16` instead but I think I was trying to avoid that changing the weight and text-transform vals too.