Revert "Display `blockquote` with larger text"

This reverts commit eff006c15e10aad0668805edbb9afb32a75ee83c.
Add basic border variables
Add basic padding variables
Don't use magic number
Don't decrease code font size
Re-set `padding-left` of `ul/ol` only on large screen
Calculate "Footnote" border width with its height
Add `%margin_after-heading` placeholder class
Don't use `$margin--mini` directly
Maintain variables

  - Fix, sort, and rename variables
  - Add padding variable for `ul` and `ol`
  - Add modifier variable for "Site Navigation" gutter
  - Add margin variable for "Main"
  - Add line-height variable for "Section Footer"
  - Add margin variable for "Article Footer"
  - Add width variable for "Drop"
  - Add width variable for "Flat UL"
  - Add padding variable for "Full Width"
  - Add margin and width variable for "Pull Quote"
Version 6.58.7