show selected rubric ratings on student grades print

the indicator wasn't showing on print if custom
ratings wer used. The indicator should be shown on
print whether or not custom ratings are used.

closes EVAL-4000
flag=none

test plan:
NO CUSTOM RATINGS:
    - create an assignment
    - add a rubric with at least 1 criterion
    - as a grader, fill out the rubric for a student
    - as a student, view the grades page and expand
        to show all details
    - print the page (or at least preview)
    - note that the selected rubric ratings have
        the line and triangle thing at the bottom

CUSTOM RATINGS:
    - set up custom ratings, or you can fake it
        - to fake it, add this as the 'customRatings'
        prop for <Ratings> in
        `ui/shard/rubrics/react/Criterion.jsx`:
        ```
            [
                {
                    "description":"Exceeds Mastery",
                    "points":4,
                    "mastery":false,
                    "color":"009688"
                },
                {
                    "description":"Mastery",
                    "points":3,
                    "mastery":true,
                    "color":"8D9900"
                },
                {
                    "description":"Near Mastery",
                    "points":2,
                    "mastery":false,
                    "color":"FAB901"
                },
                {
                    "description":"Below Mastery",
                    "points":1,
                    "mastery":false,
                    "color":"FD5D10"
                },
                {
                    "description":"Well Below Mastery",
                    "points":0,
                    "mastery":false,
                    "color":"EE0612"
                }
            ]
        ```
    - then follow the same steps as above

Change-Id: I3fb85a2ac009f5e49ce331e301fe2d9268a63cd6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/345699
Reviewed-by: Cameron Ray <cameron.ray@instructure.com>
QA-Review: Cameron Ray <cameron.ray@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>

ui/shared/rubrics/react/Ratings.jsx

@@ -62,7 +62,7 @@ export const Rating = props => {
     selected,
   } = props
 
-  const shaderStyle = {backgroundColor: tierColor}
+  const shaderStyle = selected && tierColor ? {borderBottom: `0.3em solid ${tierColor}`} : {backgroundColor: tierColor}
   const triangleStyle = {borderBottomColor: tierColor}
   const shaderClasses = classNames('shader', shaderClass)