Past Enrollment Dates are NaN on Safari

[Douglas-Hong]

In #944, we found that the dates on the x-axis in the past enrollment popup are NaN/NaN/NaN in Safari, as seen in the screenshots in https://github.com/icssc/AntAlmanac/pull/944#pullrequestreview-1926077916. The dates are correct on Chrome and Firefox, but Safari has issues.

It might be helpful to see the response we get from PeterPortal in the queryEnrollmentHistory function in enrollmentHistory.ts. It also might be helpful to look at parsedEnrollmentHistory from queryEnrollmentHistory.