Remove unneeded paragraph padding from collapsible sections
Remove unneeded paragraph padding from collapsible sections

Adding padding to the top of `p` elements in collapsible subsections
adds extra padding to govspeak components like callouts, warnings, step
numbers, etc. which makes them render incorrectly.

This margin should not be required elsewhere, because govspeak `p`
elements have bottom margin. The margin at the top is covered by
the margin introduced by the body wrapper.

alphagov/manuals-frontend,alphagov/manuals-frontend,alphagov/manuals-frontend,alphagov/manuals-frontend