Show accepted values for grades in non numeric grade scales

What does this MR do?

When the grade scale of the course is not numeric (gradeScale !== 0 ), show a warning to the instructor with the accepted values.

To do that, I expand the gradeScale and its value and in the course-grade-modal step 1, I am checking the scale type. If it's 1 or 3 (latin characters, pass/fail), I am showing the accepted values in the format name(alternateName)

This will help users identify possible errors during the grades submission

Related issues and links

Fix #295 (closed)

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