Fix spacing in one-step equation intuition

MathJax is bad and doesn't properly do spacing inside of sized things -- so \Huge{2+3} is way squishier than 2+3. We had these \quad spacers before because MathJax doesn't add the proper amount of space; now because KaTeX supports \Huge we don't need them.

Test Plan: Looked at one_step_equation_intuition.html and saw things line up.

Auditors: eater, emily