Add small margin to bottom of all Cloud pages

[nataliekwong]

There is currently no margin at the bottom of the page:

In order for the Intercom banner to render well alongside the rest of the components (and not overlap over the apply/save buttons), it would be helpful to have a margin added so that users don't have to "x" out of the banner in order to use the UI.

[octavia-squidington-iii]

cc @airbytehq/frontend