Ask Cards: Remove right-hand padding

[anselmbradford]

This right-hand margin was added in 0877172, perhaps to make the right-hand gap and the gap between the cards and search the same? At any rate, if #8401 goes ahead, the search will be full width, and removal of this padding on the cards make them align with the search on the right-hand side.

Removals

• Ask Cards: Remove right-hand padding and question-categories class.

How to test this PR

1. Visit http://localhost:8000/ask-cfpb/ and see that the right-hand gap after the cards is narrower than prod.

Screenshots

Before:

After: