Some promotion pages are miss-styled

See the following when the new theme is applied:

• https://developers.redhat.com/promotions/dot-net-core
• https://developers.redhat.com/promotions/migrating-to-microservice-databases
• https://developers.redhat.com/promotions/vertx-cheatsheet

A few minor style issues on these pages. Should be obvious to see what they are.