Remove special-case styleing for h3 in rce generated content
Remove special-case styleing for h3 in rce generated content

we had a rule that increased the top/bottom margins for h3 when
contained within content created by the user with the rce. Deleting
this rule fixes this ticket, and I can't find a reason for why the h3
would be singled out for special spacing.

closes COREFE-197

test plan:
  - using the rce html edit mode, add an h3 with some text around it
  > expect 6px margins above and below, not 24px

Change-Id: I9332c5320ea87d37d21bf84ca7a06c3e2797ea3e
Reviewed-on: https://gerrit.instructure.com/204191
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Tested-by: Jenkins
Product-Review: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>

instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms