Additional use case for global assembly padding

[jordanpagewhite]

We need to add another use case for global assembly padding. If an assembly is used at the top of the page (in position 0) and is using a background, then there should be no padding above it.

Currently we are coming across this issue across the site where there is space between the topic nav and the first assembly.

[jordanpagewhite]

Originally reported here: https://github.com/redhat-developer/developers.redhat.com/issues/3260 by @sjcox-rh Moving to the FE repo and closing the issue in the d.r.c. repo.