Fix math equations with larger font sizes
Fix math equations with larger font sizes

fixes MAT-94
flag=none

test plan:
- add some equations to rich content with text surrounding
  them
- verify that they load at the correct width
- set your font size to 18pt
- add some more equations surrounded by the larger text
- the equation widths should take care of themselves

Change-Id: Id0f5a135b63547bcd3ed44117a8d3a362dbbd254
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/266279
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
QA-Review: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
Product-Review: Nate Armstrong <619b324efbf5f7848de055bdc8bef4c0dd7c8ef5@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms